The utility of SPECT in determining the relationship between radiation dose and salivary gland dysfunction after radiotherapy.

Salivary gland scintigraphy (SGS) is used to depict salivary gland dysfunction after radiotherapy (RT). The aim of this study was to investigate the utility of SGS combined with single photon emission computed tomography (SPECT). Twenty-one patients with a carcinoma of head and neck underwent SGS before and 1 month after RT. After injection of 370 MBq 99Tcm-pertechnetate, a biplanar dynamic acquisition (12 x 1 min) was started, followed by a SPECT acquisition during 4 min. Carbachol was then injected and a second dynamic study (16 x 1 min) was performed, again followed by a SPECT acquisition. The salivary excretion fraction (SEF) was calculated both from the geometric mean planar image for each parotid and from the SPECT data for each transverse plane through the parotids. The RT-induced changes in the SEF (dSEF) were correlated with the mean radiation dose calculated using tomography-based dosimetry. The mean radiation dose to the parotids was 44 Gy (range 4.4-68.1 Gy). The mean range of the variation in radiation dose to the transverse slices within the parotids of a patient was 24 Gy (range 6.2-51.9 Gy). Considering all transverse planes through the parotids in all patients, a linear correlation was found between the dSEF calculated using SGS-SPECT and the radiation dose (r=0.45, P=0.0001). Thirteen patients had a variation in radiation dose within the parotids of more than 20 Gy. In nine of these a significant intra-individual correlation between radiation dose and the dSEF of the transverse parotid slices was found (r range 0.55-0.97; P value range 0.037-0.0001). In conclusion, SGS-SPECT can be used for monitoring radiation-induced parotid gland dysfunction. It offers the unique possibility for the assessment of intra-individual dose-dysfunction curves in patients with large variations in the radiation dose within the parotids.

Late rectal bleeding after conformal radiotherapy of prostate cancer. II. Volume effects and dose-volume histograms.

PURPOSE AND OBJECTIVE: Late rectal bleeding is a potentially dose limiting complication of three-dimensional conformal radiotherapy (3D-CRT) for prostate cancer. The frequency of late rectal bleeding has been shown to increase as the prescription dose rises above 70 Gy. The purpose of this study is to identify features of the cumulative dose-volume histogram (DVH) for the rectal wall that correlate with late rectal bleeding after 3D-CRT for prostate cancer. METHODS AND MATERIALS: Follow-up information on rectal bleeding is available for 261 and 315 patients treated using 3D-CRT at Memorial Sloan-Kettering Cancer Center for Stage T1c-T3 prostate cancer with minimum target doses of 70.2 and 75.6 Gy, respectively. All patients in this study were treated with a coplanar 6-field technique (2 lateral and 4 oblique fields). Patients were classified as having rectal bleeding if they bled (> or = Grade 2) before 30 months, and nonbleeding (< or = Grade 1) if they were without bleeding at 30 months, using the RTOG morbidity scale. Rectal bleeding was observed in 13 and 38 of the patients treated at 70.2 and 75.6 Gy, respectively. Treatment plans were analyzed for 39 nonbleeding and 13 bleeding patients receiving 70.2 Gy, and 83 nonbleeding and 36 bleeding patients receiving 75.6 Gy. Dose-volume histograms (DVHs) for the anatomic rectal wall were calculated. Average DVHs of the bleeding and nonbleeding patients were generated, and a permutation test was used to assess the significance of differences between them, for each dose group. The confounding effect of total rectal wall volume (V(RW)) was removed by calculating the average differences in DVHs between all combinations of bleeding and nonbleeding patients with similar V(RW)s. Finally, multivariate analysis using logistic regression was performed to test the significance of the DVH variables in the presence of anatomic, geometric, and medical variables previously found to correlate with rectal bleeding in a companion analysis of the same patients. RESULTS: The area under the average percent volume DVH for the rectal wall of patients with bleeding was significantly higher than those of patients without bleeding in both dose groups (p = 0.02, 70.2 Gy; p < 0.0001, 75.6 Gy). However, small V(RW)s were associated with rectal bleeding (p = 0.06, 70.2 Gy; p < 0.01, 75.6 Gy), resulting in an increase in average percent volumes exposed to all doses for patients with rectal bleeding. For patients with similar V(RW)s, rectal bleeding was significantly correlated with the volumes exposed to 46 Gy in both dose groups (p = 0.02, 70.2 Gy; p = 0.005, 75.6 Gy, tolerance in V(RW): 5 ccs). For the 75.6 Gy dose group, the percent volume receiving 77 Gy was significantly correlated with rectal bleeding (p < 0.005). Bivariate analysis using logistic regression, including V(RW) together with a single DVH variable, showed good agreement with the above analysis. Multivariate analysis revealed a borderline significant correlation of the percent volume receiving 71 Gy in the 70.2 Gy dose group. It also showed that the DVH variables were highly correlated with geometric and dosimetric variables previously found to correlate with rectal bleeding in multivariate analysis. CONCLUSION: Significant volume effects were found in the probability of late rectal bleeding for patients undergoing 3D-CRT for prostate cancer with prescription doses of 70.2 and 75.6 Gy. The percent volumes exposed to 71 and 77 Gy in the 70.2 and 75.6 Gy dose groups respectively were significantly correlated with rectal bleeding. The independent correlation of small V(RW) with rectal bleeding may indicate the existence of a functional reserve for the rectum. The independent association with larger percent volumes exposed to intermediate doses ( approximately 46 Gy) seen in both dose groups may indicate that a large surrounding region of intermediate dose may interfere with the ability to repair the effects of a central high dose region.

The impact of (18)F-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) lymph node staging on the radiation treatment volumes in patients with non-small cell lung cancer.

PURPOSE: (18)F-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) combined with computer tomography (PET-CT) is superior to CT alone in mediastinal lymph node (LN) staging in non-small cell lung cancer (NSCLC). We studied the potential impact of this non-invasive LN staging procedure on the radiation treatment plan of patients with NSCLC. PATIENTS AND METHODS: The imaging and surgical pathology data from 105 patients included in two previously published prospective LN staging protocols form the basis for the present analysis. For 73 of these patients, with positive LN's on CT and/or on PET, a theoretical study was performed in which for each patient the gross tumour volume (GTV) was defined based on CT and on PET-CT data. For each GTV, the completeness of tumour coverage was assessed, using the available surgical pathology data as gold standard. A more detailed analysis was done for the first ten consecutive patients in whom the PET-CT-GTV was smaller than the CT-GTV. Theoretical radiation treatment plans were constructed based on both CT-GTV and PET-CT-GTV. Dose-volume histograms for the planning target volume (PTV), for the total lung volume and the lung volume receiving more than 20 Gy (V(lung(20))), were calculated. RESULTS: Data from 988 assessed LN stations were available. In the subgroup of 73 patients with CT or PET positive LN's, tumour coverage improved from 75% when the CT-GTV was used to 89% with the PET-CT-GTV (P=0.005). In 45 patients (62%) the information obtained from PET would have led to a change of the treatment volumes. For the ten patients in the dosimetry study, the use of PET-CT to define the GTV, resulted in an average reduction of the PTV by 29+/-18% (+/-1 SD) (P=0.002) and of the V(lung(20)) of 27+/-18% (+/-1 SD) (P=0.001). CONCLUSION: In patients with NSCLC considered for curative radiation treatment, assessment of locoregional LN tumour extension by PET will improve tumour coverage, and in selected patients, will reduce the volume of normal tissues irradiated, and thus toxicity. This subgroup of patients could then become candidates for treatment intensification.

Quality assurance in radiotherapy by identifying standards and monitoring treatment preparation.

BACKGROUND AND PURPOSE: Due to the complexity of the treatment preparation in radiotherapy, a number of errors go undetected until after the first treatment session. Some of these errors could easily have been noticed before treatment if an objective filter existed in addition to human supervision. With this in mind, a conceptually novel extension to conventional quality assurance procedures was explored to create a global platform monitoring treatment preparation by comparison with the existing local standards. MATERIALS AND METHODS: The feasibility of developing such a platform was evaluated for a test case on a cohort of 202 patients having received breast irradiation. By statistical analysis of the treatment parameters, mean values and tolerance levels could be defined for most parameters based on the observed standard deviations. Useful correlations were traced providing us with a means to automatically track errors, the detection of which would otherwise solely depend upon the alertness of the supervisor. RESULTS AND CONCLUSIONS: Apart from its possibilities as a mere quality control tool, the platform, developed in the framework of EQUART (European Quality Assurance Program in Radiotherapy by Monitoring Treatment Preparation), can be incorporated in the treatment preparation chain, providing standard setup values for the simulation. A crucial achievement of EQUART lies in the fact that filtering out of errors occurs prior to treatment initiation.

Deep inspiration breath-hold technique for lung tumors: the potential value of target immobilization and reduced lung density in dose escalation.

PURPOSE/OBJECTIVE: This study evaluates the dosimetric benefits and feasibility of a deep inspiration breath-hold (DIBH) technique in the treatment of lung tumors. The technique has two distinct features--deep inspiration, which reduces lung density, and breath-hold, which immobilizes lung tumors, thereby allowing for reduced margins. Both of these properties can potentially reduce the amount of normal lung tissue in the high-dose region, thus reducing morbidity and improving the possibility of dose escalation. METHODS AND MATERIALS: Five patients treated for non-small cell lung carcinoma (Stage IIA-IIIB) received computed tomography (CT) scans under 4 respiration conditions: free-breathing, DIBH, shallow inspiration breath-hold, and shallow expiration breath-hold. The free-breathing and DIBH scans were used to generate 3-dimensional conformal treatment plans for comparison, while the shallow inspiration and expiration scans determined the extent of tumor motion under free-breathing conditions. To acquire the breath-hold scans, the patients are brought to reproducible respiration levels using spirometry, and for DIBH, modified slow vital capacity maneuvers. Planning target volumes (PTVs) for free-breathing plans included a margin for setup error (0.75 cm) plus a margin equal to the extent of tumor motion due to respiration (1-2 cm). Planning target volumes for DIBH plans included the same margin for setup error, with a reduced margin for residual uncertainty in tumor position (0.2-0.5 cm) as determined from repeat fluoroscopic movies. To simulate the effects of respiration-gated treatments and estimate the role of target immobilization alone (i.e., without the benefit of reduced lung density), a third plan is generated from the free-breathing scan using a PTV with the same margins as for DIBH plans. RESULTS: The treatment plan comparison suggests that, on average, the DIBH technique can reduce the volume of lung receiving more than 25 Gy by 30% compared to free-breathing plans, while respiration gating can reduce the volume by 18%. The DIBH maneuver was found to be highly reproducible, with intra breath-hold reproducibility of 1.0 (+/- 0.9) mm and inter breath-hold reproducibility of 2.5 (+/- 1.6) mm, as determined from diaphragm position. Patients were able to perform 10-13 breath-holds in one session, with a comfortable breath-hold duration of 12-16 s. CONCLUSION: Patients tolerate DIBH maneuvers well and can perform them in a highly reproducible fashion. Compared to conventional free-breathing treatment, the DIBH technique benefits from reduced margins, as a result of the suppressed target motion, as well as a decreased lung density; both contribute to moving normal lung tissue out of the high-dose region. Because less normal lung tissue is irradiated to high dose, the possibility for dose escalation is significantly improved.

Intensity-modulated tangential beam irradiation of the intact breast.

PURPOSE: To evaluate the potential benefits of intensity modulated tangential beams in the irradiation of the intact breast. METHODS AND MATERIALS: Three-dimensional treatment planning was performed on five left and five right breasts using standard wedged and intensity modulated (IM) tangential beams. Optimal beam parameters were chosen using beams-eye-view display. For the standard plans, the optimal wedge angles were chosen based on dose distributions in the central plane calculated without inhomogeneity corrections, according to our standard protocol. Intensity-modulated plans were generated using an inverse planning algorithm and a standard set of target and critical structure optimization criteria. Plans were compared using multiple dose distributions and dose volume histograms for the planning target volume (PTV), ipsilateral lung, coronary arteries, and contralateral breast. RESULTS: Significant improvements in the doses to critical structures were achieved using intensity modulation. Compared with a standard-wedged plan prescribed to 46 Gy, the dose from the IM plan encompassing 20% of the coronary artery region decreased by 25% (from 36 to 27 Gy) for patients treated to the left breast; the mean dose to the contralateral breast decreased by 42% (from 1.2 to 0.7 Gy); the ipsilateral lung volume receiving more than 46 Gy decreased by 30% (from 10% to 7%); the volume of surrounding soft tissue receiving more than 46 Gy decreased by 31% (from 48% to 33%). Dose homogeneity within the target volume improved greatest in the superior and inferior regions of the breast (approximately 8%), although some decrease in the medial and lateral high-dose regions (approximately 4%) was also observed. CONCLUSION: Intensity modulation with a standard tangential beam arrangement significantly reduces the dose to the coronary arteries, ipsilateral lung, contralateral breast, and surrounding soft tissues. Improvements in dose homogeneity throughout the target volume can also be achieved, particularly in the superior and inferior regions of the breast. It remains to be seen whether the dosimetric improvements achievable with IMRT will lead to significant clinical outcome improvements.

Quantification and predictors of prostate position variability in 50 patients evaluated with multiple CT scans during conformal radiotherapy.

PURPOSE: To determine the extent and predictors for prostatic motion in a large number of patients evaluated with multiple CT scans during radiotherapy, and evaluate the implications of these data on the design of appropriate treatment margins for patients receiving high-dose three-dimensional conformal radiotherapy. MATERIALS AND METHODS: Fifty patients underwent four serial computerized tomography (CT) scans, consisting of an initial planning scan and subsequent scans at the beginning, middle, and end of the treatment course. Each scan was performed with the patient in the prone treatment position within an immobilization device used during therapy. Contours of the prostate and seminal vesicles were drawn on the axial CT slices of each scan, and the scans were matched by alignment of the pelvic bones with a chamfer matching algorithm. Using the contour information, distributions of the displacement of the organ center of mass and organ border from the planning position were determined separately for the prostate and seminal vesicles in each of the three principle directions: anterior-posterior (AP), superior-inferior (SI) and left-right (LR). Each distribution was fitted to a normal (Gaussian) distribution to determine confidence limits in the center of mass and border displacements and thereby evaluate for the optimal margins needed to contain target motion. RESULTS: The most common directions of displacement of the prostate center of mass (COM) were in the AP and SI directions and were significantly larger than any LR movement. The mean prostate COM displacement (+/- 1 standard deviation, SD) for the entire population was -1.2 +/- 2.9 mm, -0.5 +/- 3.3 mm and -0.6 +/- 0.8 mm in the, AP and SI and LR directions respectively (negative values indicate posterior, inferior or left displacement). The mean (+/- 1 SD) seminal vesicle COM displacement for the entire population was - 1.4 +/- 4.9 mm, 1.3 +/- 5.5 mm and -0.8 +/- 3.1 mm in the AP and SI and LR directions, respectively. The data indicate a tendency for the population towards posterior displacements of the prostate from the planning position and both posterior and superior displacements of the seminal vesicles. AP movement of both the prostate and seminal vesicles were correlated with changes in rectal volume (P = 0.0014 and < 0.0001, respectively) more than with changes in bladder volume (P = 0.030 for seminal vesicles and 0.19 for prostate). A logistic regression analysis identified the combination of rectal volume > 60 cm3 and bladder volumes > 40 cm3 as the only predictor of large ( > 3 mm) systematic deviations for the prostate and seminal vesicles (P = 0.05) defined for each patient as the difference between organ position in the planning scan and mean position as calculated from the three subsequent scans. CONCLUSIONS: Prostatic displacement during a course of radiotherapy is more pronounced among patients with initial planning scans with large rectal and bladder volumes. Such patients may require more generous margins around the CTV to assure its enclosure within the prescription dose region. Identification and correction of patients with large systematic errors will minimize the extent of the margin required and decrease the volume of normal tissue exposed to higher radiation doses.

Computerized design of target margins for treatment uncertainties in conformal radiotherapy.

PURPOSE: We describe a computerized method of determining target margins for beam aperture design in conformal radiotherapy plans. MATERIALS AND METHODS: The method uses previously measured data from a population of patients to simulate setup error and organ motion in the patient currently being planned. Starting with a clinical target volume (CTV) and nontarget organs from the patient's planning CT scan, the simulation is repeated many times to produce a spatial probability distribution for each organ in the treatment machine coordinate system. This is used to determine a prescribed dose volume (PDV), defined as the volume to receive the prescribed dose, which encompasses the CTV while restricting the volume of nontarget organs within it, according to planner-specified values. The PDV is used to design beam apertures using a conventional margin for beam penumbra. RESULTS: The method is applied to 6-field prostate conformal treatment plans, in which the PDV encloses the prostate and seminal vesicles while limiting the enclosed rectal wall volume. The effect of organ motion is assessed by applying the plans on subsequent CT scans of the same patients, calculating probabilities for tumor control (TCP) and normal tissue complication (NTCP), and comparing with plans designed from a physician-drawn planning target volume (PTV). Although prostate TCP and rectal wall NTCP are found to be similar in the two sets of plans, TCP for the seminal vesicles is significantly higher in the PDV-based plans. CONCLUSIONS: The method can improve the dose conformality of treatment plans by incorporating population-based measurements of treatment uncertainties and consideration of nontarget tissues in the design of nonuniform target margins.

Locally advanced prostatic cancer: long-term toxicity outcome after three-dimensional conformal radiation therapy--a dose-escalation study.

PURPOSE: To determine the long-term effects of 75.6- and 81.0-Gy doses of three-dimensional conformal radiation therapy in a dose-escalation study in patients with stage T2c-T3 prostatic cancer. MATERIALS AND METHODS: Fifty patients received an initial 75.6-Gy dose, and the dose in 46 patients was subsequently escalated to 81.0-Gy. Median follow-up was 60 and 40 months, respectively. RESULTS: The rates of effects of acute toxicity during the course of treatment were similar for both dose levels. Among the 96 patients, the rate of grade 2 morbidities necessitating medication to relieve acute symptoms was 17% (16 patients) for rectal and 36% (35 patients) for urinary morbidities. All other patients had either no or grade 1 morbidities. Fourteen patients (15%) developed late grade 2 rectal morbidities. There were no differences in 5-year actuarial rates of late grade 2 rectal or urinary morbidities among patients who received 75.6 Gy versus those who received 81.0 Gy. One patient treated with 81.0 Gy developed a grade 3 urethral stricture, which was resolved with dilatation. CONCLUSION: Tumor dose escalation beyond conventional radiation doses for localized prostatic cancer is feasible when delivered with three-dimensional conformal radiation therapy, with no increase in morbidity in normal tissue.

Dose escalation with three-dimensional conformal radiation therapy affects the outcome in prostate cancer.

PURPOSE: Three-dimensional conformal radiation therapy (3D-CRT) is a technique designed to deliver prescribed radiation doses to localized tumors with high precision, while effectively excluding the surrounding normal tissues. It facilitates tumor dose escalation which should overcome the relative resistance of tumor clonogens to conventional radiation dose levels. The present study was undertaken to test this hypothesis in patients with clinically localized prostate cancer. METHODS AND MATERIALS: A total of 743 patients with clinically localized prostate cancer were treated with 3D-CRT. As part of a phase I study, the tumor target dose was increased from 64.8 to 81 Gy in increments of 5.4 Gy. Tumor response was evaluated by post-treatment decrease of serum prostate-specific antigen (PSA) to levels of < or = 1.0 ng/ml and by sextant prostate biopsies performed > or = 2.5 years after completion of 3D-CRT. PSA relapse-free survival was used to evaluate long-term outcome. The median follow-up was 3 years (range: 1-7.6 years). RESULTS: Induction of an initial clinical response was dose-dependent, with 90% of patients receiving 75.6 or 81.0 Gy achieving a PSA nadir < or = 1.0 ng compared with 76% and 56% for those treated with 70.2 Gy and 64.8 Gy, respectively (p < 0.001). The 5-year actuarial PSA relapse-free survival for patients with favorable prognostic indicators (stage T1-2, pretreatment PSA < or = 10.0 ng/ml and Gleason score < or = 6) was 85%, compared to 65% for those with intermediate prognosis (one of the prognostic indicators with a higher value) and 35% for the group with unfavorable prognosis (two or more indicators with higher values) (p < 0.001). PSA relapse-free survival was significantly improved in patients with intermediate and unfavorable prognosis receiving > or = 75.6 Gy (p < 0.05). A positive biopsy at > or = 2.5 years after 3D-CRT was observed in only 1/15 (7%) of patients receiving 81.0 Gy, compared with 12/25 (48%) after 75.6 Gy, 19/42 (45%) after 70.2 Gy, and 13/23 (57%) after 64.8 Gy (p < 0.05). CONCLUSIONS: The data provide evidence for a significant effect of dose escalation on the response of human prostate cancer to irradiation and defines new standards for curative radiotherapy in this disease.

Three-dimensional conformal radiotherapy and dose escalation: where do we stand?

Three-dimensional conformal radiotherapy is an effective means of delivering high doses of radiation with enhanced precision. Several institutions have gained substantial experience using this modality for patients with clinically localized prostate cancer. Reports from these centers have demonstrated not only excellent tolerance despite the administration of higher radiation doses, but improved biochemical and local control outcomes as well. Meticulous attention to treatment technique and dose volume histogram analysis are critical for the safe implementation of these higher doses. The emergence of intensity-modulated treatment planning has provided the opportunity at our institution to further escalate the radiation dose to 86.4 Gy while still respecting the surrounding normal tissue tolerance. Phase I studies will need to continue to define more clearly the maximal dose of radiation that can be delivered safely with this modality. Current studies indicate a direct correlation between dose and prostate-specific antigen (PSA) relapse-free survival response for patients with intermediate and high-risk prognostic features. These patients likely represent the ideal cohort for future studies designed to investigate the impact of dose on biochemical and disease-free survival outcome.

Variation in prostate position quantitation and implications for three-dimensional conformal treatment planning.

PURPOSE: This study describes and quantitates the motion, i.e., variation in position, of the prostate within the pelvis and its effect on target and normal organ dose. METHODS AND MATERIALS: The motion of the planning target volume (PTV) borders and center of mass was studied in 13 patients with carcinoma of the prostate through the use of superimposed serial computerized tomography (CT) scans. Changes in bladder and rectal volumes were measured and their relationship to displacements of the PTV position were noted. The effects of this motion on target and normal organ doses were measured. RESULTS: A variability in the position of the PTV is seen over time, which is related to changes in bladder and rectal volumes. The one standard deviation displacements of the PTV center of mass with respect to the planning scan center of mass position were 0.12, 0.40, and 0.31 cm in the lateral, anterior-posterior, and superior-inferior directions, respectively. Movement was significantly larger in the superior part of the PTV above the base of the bladder than in the inferior part. Movement of the borders of the PTV outward from the patient axis; hence, toward the edges of the treatment field, was also examined. Outward displacements of the anterior target border below the base of the bladder were less than 0.3 cm in 90% of the cases, and 1.4 cm above the bladder base. For the posterior wall these displacements were less than 0.7 cm and 1.1 cm, respectively, whereas the lateral border displacements were less than 0.3 cm throughout (90% confidence limits). These displacements would cause a median of 6% of the PTV to receive less than 95% of the planned dose for any given treatment day in these patients; the effect on rectal and bladder wall doses was greater and true doses may not be measurable through the use of only one treatment planning CT scan. CONCLUSIONS: The prostate is not a static organ, but rather has some limited motion in the pelvis secondary to bladder and rectal volume changes. This motion has been quantified for a group of patients, and may provide a guide to further studies on the placement of field borders.

Measurement of patient positioning errors in three-dimensional conformal radiotherapy of the prostate.

PURPOSE/OBJECTIVE: To determine the spatial distribution of setup errors for patients treated with six-field, three-dimensional (3D) conformal radiation therapy for prostate cancer. METHODS AND MATERIALS: Port films for 50 patients were analyzed retrospectively. The port films were digitized and compared, using image registration software, to simulator films (representing the ideal treatment position). Patient positioning uncertainty for a given setup was determined using port films from three projections, two obliques, and one lateral. A total of 1239 port films and 300 simulator films were analyzed for the study. Patient position was analyzed for out-of-plane rotations and time trends over the course of treatment. RESULTS: The distribution of systematic setup errors for the 50 patients, defined as the mean patient displacement for the treatment course, had a mean and standard deviation (SD) of (-0.1 +/- 1.9) mm, (0.4 +/- 1.4) mm, and (-0.3 +/- 1.3) mm in the mediolateral (ML), superior-inferior (SI) and anterior-posterior (AP) directions, and (-0.1 +/- 0.2) for rotational errors. The distribution of random setup errors about the mean approximated a normal distribution and the standard deviations for the population of patients in the ML, SI, and AP directions, were 2.0 mm, 1.7 mm, and 1.9 mm, respectively. The distribution of out-of-plane rotations had 1 SD of 0.9 degrees and 0.6 degrees about the SI and AP axes. Ten of the 50 patients demonstrated a statistically significant time trend in their setup position resulting in shifts ranging from 2 to 7 mm. CONCLUSIONS: The setup verification protocol appears to minimize systematic setup errors to a level that approaches the sensitivity of the image registration technique. The random day to day fluctuations, represented by the average values of the standard deviations, are minor in comparison to the currently used margins, which further emphasizes the effectiveness of this protocol in conjunction with the use of the immobilization device.

The effect of treatment positioning on normal tissue dose in patients with prostate cancer treated with three-dimensional conformal radiotherapy.

PURPOSE: To prospectively assess the effect of supine vs. prone treatment position on the dose to normal tissues in prostate cancer patients treated with the three-dimensional conformal technique. METHODS AND MATERIALS: Twenty-six patients underwent three-dimensional treatment planning in both the supine and prone treatment positions. The planning target volume and normal tissue structures were outlined on each CAT scan slice, and treatment plans were compared to assess the effect of treatment position on the volume of rectum, bladder, and bowel exposed to the high dose of irradiation. RESULTS: The average dose to the rectal wall and the V95 (volume of rectal wall receiving at least 95% of the prescription dose) for the prone position were 64 and 24% of the prescription dose, respectively, compared to 72 and 29%, respectively, for the supine position (p < 0.05). When the average rectal wall dose was used as an endpoint, 14 of the 26 patients (54%) had an advantage for the prone position compared to 1 (4%) who demonstrated an advantage for the supine position (p < 0.0002). Similarly, when V95 of the rectal wall was used as a measure of comparison, 15 patients (58%) had an advantage for the prone position compared to 1 (4%) who demonstrated an advantage for the supine position (p < 0.0002). In 13 patients (50%), a change from supine to the prone position was associated with reduction of the V95 to levels < 30% of the prescription dose compared to 3 patients (11%) in whom such an advantage resulted from change of the prone to the supine position (p < 0.005). The effect of treatment position on the rectal wall dose was most pronounced in the region of the seminal vesicles. An increased volume of bowel was also noted in the supine position. The treatment position, however, had no significant impact on the dose to the bladder wall. CONCLUSIONS: Three-dimensional conformal radiotherapy for prostate cancer in the prone position is associated with significant reduction of the dose to the rectum and bowel resulting in an improvement in the therapeutic ratio.

Treatment planning for primary breast cancer: a patterns of care study.

PURPOSE: The 1989 Patterns of Care Study included treatment planning for early breast cancer. A Consensus Committee of radiation physicists and oncologists determined current guidelines and developed questionnaires to determine treatment planning and delivery processes used by the participating institutions (e.g., use of portal films). This article presents and analyzes the results of that survey. METHODS AND MATERIALS: The survey included 449 respondents, distributed as follows: 136 (30%) from Strata I (academic facilities); 169 (38%) from Strata II (hospital based facilities); and 144 (32%) from Strata III (freestanding facilities). The treatment planning procedures surveyed included: whether individualized tissue compensators are used, whether inhomogeneity corrections are used in dose calculations, the use of computerized tomography, whether isodose distributions for external beam tangents and interstitial implants are generated, the use of lymphoscintigraphy, immobilization devices, simulations, portal films, etc. RESULTS: The survey results demonstrated that out of 305 patients from Strata I and II institutions, 237 (78%) had simulated tangential fields. Consistent with this finding is that 76% of patients from Strata I and II institutions were immobilized, while only 51% of Strata III patients were. Moreover, only 18 out of the 449 (4%) of cases did not have any type of external beam dose distribution calculated--presumably, in these cases missing tissue compensation would be unlikely. On the other hand, 41% of the Strata II, 27% of Strata III, but only 19% of Strata I (p < 0.0002) cases received CT. Surprisingly, 19% of the Strata I, 35% of the Strata II, and 25% of the Strata III (p = 0.0011) patients received lymphoscintigraphy, perhaps reflecting the use of wide tangents to encompass the internal mammary nodes in these patients. In terms of optimizing treatments, 74% of Strata I, 70% of Strata II, and 78% of Strata III patients had wedges used on both tangential fields, although in 5, 12, and 14%, respectively, no beam modification of any sort was used. Furthermore, it should be noted that in 7% of the Strata I, 23% of Strata II, and 37% of Strata III cases there was no attempt to reduce the divergence of the tangential fields into the lung. On the other hand, if one considers the 135 (of 449) patients where matching of the tangential and supraclavicular fields was applicable, 41% of Strata I, 22% of Strata II and 46% of Strata III patients had those fields matched in a vertical plane, which would involve sophisticated alignment procedures. Quality control of treatment delivery was high: 97% of all surveyed received portal films at least once. The use of thermoluminescent dosimetry (TLD) to measure the dose to the contralateral breast was of little interest: only 4 of the 305 Strata I and II patients received in vivo measurements. CONCLUSIONS: This national survey has established the patterns of treatment planning for early breast cancer. It shows a generally consistent approach-although a number of statistically significant variations have been identified.

Conformal radiation treatment of prostate cancer using inversely-planned intensity-modulated photon beams produced with dynamic multileaf collimation.

PURPOSE: To implement radiotherapy with intensity-modulated beams, based on the inverse method of treatment design and using a multileaf collimation system operating in the dynamic mode. METHODS AND MATERIALS: An algorithm, based on the inverse technique, has been integrated into the radiotherapy treatment-planning computer system in our Center. This method of computer-assisted treatment design was used to derive intensity-modulated beams to optimize the boost portion of the treatment plan for a patient with a T1c cancer of the prostate. A dose of 72 Gy (in 40 fractions) was given with a six-field plan, and an additional 9 Gy (in five fractions) with six intensity-modulated beams. The intensity-modulated fields were delivered using dynamic multileaf collimation, that is, individual leaves were in motion during radiation delivery, with the treatment machine operating in the clinical mode. Exhaustive quality assurance measurement and monitoring were carried out to ensure safe and accurate implementation. RESULTS: Dose distribution and dose-volume histogram of the "inverse method" boost plan and of the composite (72 Gy primary + 9 Gy boost) plan were judged clinically acceptable. Compared to a manually designed boost plan, the inverse treatment design gave improved conformality and increased dose homogeneity in the planning target volume. Film and ion chamber dosimetry, performed prior to the first treatment, indicated that each of the six intensity-modulated fields was accurately produced. Thermoluminescent dosimeter (TLD) measurements performed on the patient confirmed that the intended dose was delivered in the treatment. In addition, computer-aided treatment-monitoring programs assured that the multileaf collimator (MLC) position file was executed to the specified precision. In terms of the overall radiation treatment process, there will likely be labor savings in the planning and the treatment phases. CONCLUSIONS: We have placed into clinical use an integrated system of conformal radiation treatment that incorporated the inverse method of treatment design and the use of dynamic multileaf collimation to deliver intensity-modulated beams. The system can provide better treatment design, which can be implemented reliably and safely. We are hopeful that improved treatment efficacy will result.

A method of incorporating organ motion uncertainties into three-dimensional conformal treatment plans.

PURPOSE: We describe a method of incorporating organ motion into three-dimensional (3D) conformal treatment plans, which predicts the effect of organ motion on the calculated dose to both the clinical target volume (CTV) and nontarget organs. METHODS AND MATERIALS: The method is based on measurements of organ motion by means of multiple computed tomography (CT) scans from a group of "reference" patients, in which the data consist of previously drawn contours of the target and nontarget organs. A computer program records the differences in contour position and shape that occur between scans in the reference data, and according to those differences adjusts the contours and dose calculation points of a "study" patient currently being planned, thus simulating organ motion. Dose-volume histograms (DVHs) are accumulated, and the process is repeated over the set of reference patient scans, resulting in a set of treatment plans that are ranked according to a dose-based endpoint. Two plans are selected corresponding to specified lower and upper confidence limits in the endpoint, and the DVHs from these plans are displayed for comparison with the DVHs from the nominal plan in the absence of motion. RESULTS: As an example of the method's use, it is applied to a 6-field conformal treatment plan for prostate cancer. Confidence limit DVHs of the CTV and rectal wall (in which the plans were ranked by probabilities for tumor control and normal tissue complication, respectively) are presented and compared to those from the nominal plan. CONCLUSION: The method provides a means of estimating the uncertainty in dose delivered by a treatment plan when organ motion is present. It is generally applicable to any treatment site for which data in the form of multiple CT scans are available, and can be extended to include other treatment uncertainties such as variation in patient positioning.