11C-acetate PET/CT before radical prostatectomy: nodal staging and treatment failure prediction.

UNLABELLED: Despite early detection programs, many patients with prostate cancer present with intermediate- or high-risk disease. We prospectively investigated whether (11)C-acetate PET/CT predicts lymph node (LN) metastasis and treatment failure in men for whom radical prostatectomy is planned. METHODS: 107 men with intermediate- or high-risk localized prostate cancer and negative conventional imaging findings underwent PET/CT with (11)C-acetate. Five underwent LN staging only, and 102 underwent LN staging and prostatectomy. PET/CT findings were correlated with pathologic nodal status. Treatment-failure-free survival was estimated by the Kaplan-Meier method. The ability of PET/CT to predict outcomes was evaluated by multivariate Cox proportional hazards analysis. RESULTS: PET/CT was positive for pelvic LN or distant metastasis in 36 of 107 patients (33.6%). LN metastasis was present histopathologically in 25 (23.4%). The sensitivity, specificity, and positive and negative predictive values of PET/CT for detecting LN metastasis were 68.0%, 78.1%, 48.6%, and 88.9%, respectively. Treatment failed in 64 patients: 25 with metastasis, 17 with a persistent postprostatectomy prostate-specific antigen level greater than 0.20 ng/mL, and 22 with biochemical recurrence (prostate-specific antigen level > 0.20 ng/mL after nadir) during follow-up for a median of 44.0 mo. Treatment-failure-free survival was worse in PET-positive than in PET-negative patients (P < 0.0001) and in those with false-positive than in those with true-negative scan results (P < 0.01), suggesting that PET may have demonstrated nodal disease not removed surgically or identified pathologically. PET positivity independently predicted failure in preoperative (hazard ratio, 3.26; P < 0.0001) and postoperative (hazard ratio, 3.07; P = 0.0001) multivariate models. CONCLUSION: In patients planned for or completing prostatectomy, (11)C-acetate PET/CT detects LN metastasis not identified by conventional imaging and independently predicts treatment-failure-free survival.

18F-fluorodeoxyglucose-positron emission tomography and pathologic tumor size in early-stage invasive cervical cancer.

PURPOSE: Cervical cancer tumor size determined by 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET) thresholding of the maximum standardized uptake value (SUVMax) has been correlated with the determined tumor size by computed tomography and magnetic resonance imaging. The purpose of this study was to evaluate the relationship between preoperative FDG-PET tumor size and pathologic tumor diameter in patients with early-stage cervical cancer who were undergoing radical hysterectomy. PATIENTS AND METHODS: Forty patients with early-stage cervical cancer underwent pretreatment FDG-PET/computed tomography before radical hysterectomy and lymph node dissection. Primary tumor diameter was defined on FDG-PET as the largest diameter of the 3-dimensional volumetric isocontour of the 40% threshold of the SUVMax. The FDG-PET measurements were compared with the tumor diameter and the histological diameter of the pathologic specimen using regression analysis, paired t test, and unpaired t test. RESULTS: The FDG-PET tumor diameter measurements were correlated to the pathologic tumor diameter in the surgical specimen with a coefficient of determination (R2) of 0.951 and a correlation coefficient of 0.757 (P < 0.0001). CONCLUSION: There is a high level of correlation in the FDG-PET and the pathologic tumor measurements in the early-stage cervical cancer.

18-F-fluorodeoxyglucose-positron emission tomography evaluation of early metabolic response during radiation therapy for cervical cancer.

PURPOSE: To document changes in cervical tumor (18)-F-fluorodeoxyglocose (FDG) uptake during radiation therapy and to correlate those changes with post-treatment tumor response and survival outcome. METHODS AND MATERIALS: A total of 36 patients with Stage Ib1 to IIIb cervical cancer were enrolled in an institutional protocol examining the use of fluorodeoxyglucose-positron emission tomography (FDG-PET) for brachytherapy treatment planning. As part of this study, FDG-PET or PET/computed tomograpy (CT) images were obtained before, during, and after the completion of radiation therapy. Tumor metabolic responses were assessed qualitatively and semi-quantitatively by measurement of the maximal standardized uptake value (SUV(max)). RESULTS: Post-treatment FDG-PET images were obtained for 36 patients in this study. Of the patients, 29 patients had a complete metabolic response on the post-treatment PET, 4 had a partial metabolic response, and 3 had new sites of FDG uptake. Six patients had a complete metabolic response observed during radiation therapy, 26 had a partial metabolic response and 4 had stable or increased tumor metabolic activity. For patients with complete metabolic response during radiation therapy, median time to complete response was 29.5 days (range, 18-43 days). The mean cervical tumor SUV(max) decreased from 11.2 (SD, 6.3; range, 2.1-38.0) pretreatment to 2.4 (SD, 2.7; range, 0-8.8) mid treatment, and 0.5 (SD, 1.7; range, 0-8.3) post-treatment. CONCLUSIONS: During radiation therapy for cervical cancer, FDG-PET can be used to monitor treatment response. Complete metabolic response during radiation therapy was observed for a subset of patients. Recommendations regarding the optimal timing of FDG-PET during treatment for cervical cancer will require further systematic study.

Adaptive brachytherapy treatment planning for cervical cancer using FDG-PET.

PURPOSE: A dosimetric study was conducted to compare intracavitary brachytherapy using both a conventional and a custom loading intended to cover a positron emission tomography (PET)-defined tumor volume in patients with cervix cancer. METHODS AND MATERIALS: Eleven patients who underwent an [(18)F]-fluoro-deoxy-D-glucose (FDG)-PET in conjunction with their first, middle, or last brachytherapy treatment were included in this prospective study. A standard plan that delivers 6.5 Gy to point A under ideal conditions was compared with an optimized plan designed to conform the 6.5-Gy isodose surface to the PET defined volume. RESULTS: A total of 31 intracavitary brachytherapy treatments in conjunction with an FDG-PET were performed. The percent coverage of the target isodose surface for the first implant with and without optimization was 73% and 68% (p = 0.21). The percent coverage of the target isodose surface for the mid/final implant was 83% and 70% (p = 0.02), respectively. The dose to point A was higher with the optimized plans for both the first implant (p = 0.02) and the mid/last implants (p = 0.008). The dose to 2 cm(3) and 5 cm(3) of both the bladder and rectum were not significantly different. CONCLUSIONS: FDG-PET based treatment planning allowed for improved dose coverage of the tumor without significantly increasing the dose to the bladder and rectum.

Nuclear medicine/radiology training and certification requirements recent changes.

RATIONALE AND OBJECTIVES: There have been many recent changes in governmental regulations affecting nuclear medicine/nuclear radiology practice and training requirements. This article summarizes the background for these changes, and summarizes the new requirements for residency training, board certification, and authorized user status.

FDG-PET imaging for the assessment of physiologic volume response during radiotherapy in cervix cancer.

PURPOSE: To evaluate the physiologic tumor volume response during treatment in cervical cancer using 18F-fluorodeoxyglucose positron emission tomography (FDG-PET). PATIENTS AND METHODS: This was a prospective study of 32 patients. Physiologic tumor volume in cubic centimeters was determined from the FDG-PET images using the 40% threshold method. RESULTS: The mean pretreatment tumor volume was 102 cm3. The mean volume by clinical Stages I, II, and III were 54, 79, and 176 cm3, respectively. After 19.8 Gy external irradiation to the pelvis, the reduction in tumor volume was 29% (72 cm3). An additional 13 Gy from high-dose-rate (HDR) brachytherapy reduced the mean volume to 15.4 cm3, and this was subsequently reduced to 8.6 cm3 with 13 Gy additional HDR brachytherapy (26 Gy, HDR). Four patients had physiologic FDG uptake in the cervix at 3 months after the completion of therapy. The mean time to the 50% reduction in physiologic tumor volume was 19.9 days and after combined external irradiation and HDR to 24.9 Gy. CONCLUSION: These results indicate that physiologic tumor volume determination by FDG-PET is feasible and that a 50% physiologic tumor volume reduction occurs within 20 days of starting therapy.

F-18 fluorodeoxyglucose uptake in primary cervical cancer as an indicator of prognosis after radiation therapy.

PURPOSE: We evaluated the prognostic significance of tumor metabolic activity on pretreatment positron emission tomography using the glucose analog F-18 fluorodeoxyglucose (FDG-PET) in patients with carcinoma of the cervix undergoing radiotherapy with or without concurrent chemotherapy. METHODS: We studied 96 consecutive patients who underwent FDG-PET prior to initiation of radiotherapy with or without concurrent chemotherapy for carcinoma of the cervix. Pretreatment FDG uptake of the primary tumor was assessed with the semiquantitative standardized uptake value (SUV) and correlated with disease-free and overall survival. Survival was estimated by the Kaplan-Meier method. Univariate and multivariate analyses were performed with the logistic likelihood ratio test and the Cox proportional hazards model, respectively. RESULTS.: Five-year disease-free survivals in patients with maximal SUV <10.2 and > or =10.2 were 71% and 52% (P = 0.0289) respectively, while overall survivals were 72% and 69% (P = 0.4), respectively. On multivariate analysis, lymph node metastasis on FDG-PET was found to be predictive of disease-free survival (P < 0.0001). Both the SUV for FDG and FIGO Stage I disease were found to be marginally predictive of disease-free survival (P = 0.055 and P = 0.058, respectively). CONCLUSIONS: FDG uptake within primary cervical cancer, as measured by SUV, is predictive of disease-free survival in patients undergoing radiotherapy for cervical cancer. High FDG uptake may be useful in identifying patients who may require more aggressive initial therapy.

Sequential FDG-PET brachytherapy treatment planning in carcinoma of the cervix.

PURPOSE: To evaluate the utility of sequential (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) imaging for brachytherapy treatment planning in patients with carcinoma of the cervix. METHODS AND MATERIALS: Twenty-four patients with carcinoma of the cervix were included in this prospective study. The clinical stage of their disease was Ib (7), IIa (1), IIb (7), and IIIb (9). Patients were treated with irradiation and brachytherapy, with the majority receiving concurrent weekly cisplatin chemotherapy. Patients underwent diagnostic FDG-PET imaging before treatment, sequential FDG-PET brachytherapy imaging during treatment, and diagnostic FDG-PET 3 months after treatment completion. Delineation of the gross tumor volume, bladder, and rectum was performed for all scans using a commercially available treatment-planning system. Actual treatment delivery was based on two-dimensional orthogonal planning. RESULTS: The mean gross tumor volume and percent coverage by the target isodose surface for the initial, mid, and last implant were 37 cm3, 17 cm3, and 10 cm3 and 68%, 76%, and 79%, respectively. Nine of 11 patients were found to have continued decrease in tumor volume as measured by FDG-PET, with 3 patients having complete regression of their tumor before treatment was completed. The maximal bladder and rectal doses obtained from three-dimensional dose-volume histograms were significantly higher than the International Commission on Radiation Units and Measurements Report 38 bladder and rectal points obtained by two-dimensional treatment-planning. CONCLUSIONS: Sequential FDG-PET brachytherapy imaging identifies the tumor response in individual patients, potentially making patient-specific brachytherapy treatment planning possible.

A treatment planning study comparing HDR and AGIMRT for cervical cancer.

The customization of brachytherapy dose distributions for gynecologic malignancies is limited by the spatial positioning of the applicators. We tested the hypothesis that applicator-guided intensity modulated radiation therapy (AGIMRT) has the potential to deliver highly conformal dose distributions to cervical tumors, representing improvement over distributions obtained with intracavitary brachytherapy. A commercial three-dimensional (3-D) treatment planning system was used to create plans for ten cervical cancer patients treated at our institution. Dose distributions of conventionally designed high dose rate (HDR) plans were compared against those of AGIMRT. Tumor delineation was based on a previously published binary threshold technique, using image intensity on positron emission tomography (PET) scans. AGIMRT treatment schedules were designed using two fraction sizes: 6.5 Gy, to directly reproduce the HDR fractionation, and 1.8 Gy, to simulate traditional external beam fractionation. The average minimum tumor dose was significantly greater for the AGIMRT dose distributions than for the HDR distributions (64.2 Gy vs 33.6 Gy; p = 0.005). The mean percent tumor volume at the prescription dose was higher for the AGIMRT plans (90.0% vs 58.2%; p = 0.005). Using AGIMRT, the mean percent volume at the tolerance limit was decreased for the bladder (6.1% vs 16.6%; p = 0.047) but increased for the rectum (4.1% vs 2.2%; p = 0.646). Our study suggests that there may be conceptual and dosimetric advantages to replacing HDR with AGIMRT for patients with large-volume cervical tumors. This investigation is being expanded using sequential PET images to model tumor regression and compare brachytherapy and AGIMRT throughout the course of therapy.

Impact of FDG-PET on radiation therapy volume delineation in non-small-cell lung cancer.

PURPOSE: Locoregional failure remains a significant problem for patients receiving definitive radiation therapy alone or combined with chemotherapy for non-small-cell lung cancer (NSCLC). Positron emission tomography (PET) with [(18)F]fluoro-2-deoxy-d-glucose (FDG) has proven to be a valuable diagnostic and staging tool for NSCLC. This prospective study was performed to determine the impact of treatment simulation with FDG-PET and CT on radiation therapy target volume definition and toxicity profiles by comparison to simulation with computed tomography (CT) scanning alone. METHODS: Twenty-six patients with Stages I-III NSCLC were studied. Each patient underwent sequential CT and FDG-PET simulation on the same day. Immobilization devices used for both simulations included an alpha cradle, a flat tabletop, 6 external fiducial markers, and a laser positioning system. A radiation therapist participated in both simulations to reproduce the treatment setup. Both the CT and fused PET/CT image data sets were transferred to the radiation treatment planning workstation for contouring. Each FDG-PET study was reviewed with the interpreting nuclear radiologist before tumor volumes were contoured. The fused PET/CT images were used to develop the three-dimensional conformal radiation therapy (3DCRT) plan. A second physician, blinded to the results of PET, contoured the gross tumor volumes (GTV) and planning target volumes (PTV) from the CT data sets, and these volumes were used to generate mock 3DCRT plans. The PTV was defined by a 10-mm margin around the GTV. The two 3DCRT plans for each patient were compared with respect to the GTV, PTV, mean lung dose, volume of normal lung receiving > or =20 Gy (V20), and mean esophageal dose. RESULTS: The FDG-PET findings altered the AJCC TNM stage in 8 of 26 (31%) patients; 2 patients were diagnosed with metastatic disease based on FDG-PET and received palliative radiation therapy. Of the 24 patients who were planned with 3DCRT, PET clearly altered the radiation therapy volume in 14 (58%), as follows. PET helped to distinguish tumor from atelectasis in all 3 patients with atelectasis. Unsuspected nodal disease was detected by PET in 10 patients, and 1 patient had a separate tumor focus detected within the same lobe of the lung. Increases in the target volumes led to increases in the mean lung dose, V20, and mean esophageal dose. Decreases in the target volumes in the patients with atelectasis led to decreases in these normal-tissue toxicity parameters. CONCLUSIONS: Radiation targeting with fused FDG-PET and CT images resulted in alterations in radiation therapy planning in over 50% of patients by comparison with CT targeting. The increasing availability of integrated PET/CT units will facilitate the use of this technology for radiation treatment planning. A confirmatory multicenter, cooperative group trial is planned within the Radiation Therapy Oncology Group.

Treatment planning guidelines regarding the use of CT/PET-guided IMRT for cervical carcinoma with positive paraaortic lymph nodes.

PURPOSE: Computed tomography (CT)/positron emission tomography (PET)-guided intensity-modulated radiotherapy of the paraaortic lymph nodes (PALNs) has been proposed for patients with cervical carcinoma and paraaortic metastasis. This investigation attempted to determine the guidelines regarding the selection of appropriate treatment parameters (e.g., number of beams, beam geometry) and organ-specific parameters (e.g., importance weighting and tolerance dose) for intensity-modulated radiotherapy planning for the PALNs. METHODS AND MATERIALS: Patients underwent imaging using CT and PET. The images were registered, and the structures were contoured. A goal dose of 50.4 Gy and 59.4 Gy was assigned to the clinical target volume (lymph node bed) and gross tumor volume (PET-delineated PALNs), respectively. For each patient, multiple treatment plans using various beam geometries and planning parameters were executed and evaluated in terms of the dose-volume histograms of the target and critical structures. RESULTS: Acceptable sparing of the stomach, liver, and colon was achieved, regardless of the number of beams used. Sparing of the spinal cord was strongly dependent on the number and arrangement of the beams. Varying the number and arrangement of the beams affected small intestine sparing, but the amount of sparing was limited because the small intestine overlapped the target volumes, and, therefore, received the prescription dose. Adjusting the number of beams, beam angles, and prescription parameters provided minimal improvement in kidney sparing. CONCLUSION: We successfully developed treatment plans that deliver 59.4 Gy to the positive PALNs and 50.4 Gy to the paraaortic region using CT/PET-guided intensity-modulated radiotherapy.

11C-acetate PET imaging of prostate cancer: detection of recurrent disease at PSA relapse.

UNLABELLED: Patients with rising prostate-specific antigen (PSA) levels after definitive local therapy of prostate carcinoma present a diagnostic dilemma. A local recurrence would be amenable to additional local therapy with curative intent, whereas metastatic disease would require palliative androgen ablation therapy. In this study, we evaluated the effectiveness of PET with (11)C-acetate (AC PET) for evaluation of patients with rising PSA after radical prostatectomy or radiation therapy. We also compared the reliability of AC PET in detecting recurrent prostate cancer with that of PET with (18)F-FDG. METHODS: Two groups of patients with PSA recurrence were enrolled in this study: group A, 30 patients after prostatectomy, and group B, 16 patients after radiation therapy. After administration of 1,110 MBq (30 mCi) of (11)C-acetate, whole-body PET images were obtained. After allowing for (11)C decay, 555 MBq (15 mCi) of (18)F-FDG were administered and repeated whole-body imaging was performed. The PET findings were scored as positive or negative in each of the following regions: prostatic bed, pelvic nodes, paraaortic nodes, and other sites (bone or soft tissue). PET findings were correlated with those of CT, bone scintigraphy, and biopsy. RESULTS: Twenty-seven of 46 AC PET studies (59%) had positive findings, whereas only 8 (18)F-FDG PET studies had positive findings (17%). Limiting the analysis to patients with findings confirmed by CT, bone scintigraphy, or biopsy or considered highly likely to represent tumor, 14 (30%) had disease identified by AC PET, whereas only 4 (9%) had disease identified by (18)F-FDG PET. CT was performed on 22 patients and had positive findings in 3 (14%). Thirteen of 22 patients (59%) with serum PSA > 3 ng/mL had positive AC PET findings, whereas only 1 of 24 patients (4%) with serum PSA levels < or = 3 ng/mL had positive findings. CONCLUSION: AC PET demonstrates marked uptake in prostate cancer and has higher sensitivity than (18)F-FDG PET. These preliminary data show that (11)C-acetate is a promising tracer for detection of recurrent prostate cancer.

Improved prognostic value of 18F-FDG PET using a simple visual analysis of tumor characteristics in patients with cervical cancer.

UNLABELLED: In patients with cervical cancer, it is important to estimate prognosis at the time of diagnosis. This study using PET with (18)F-FDG was undertaken to determine whether a simple and fast visual analysis of characteristics of the primary tumor before initiation of treatment could achieve this goal. METHODS: Forty-seven patients with cervical cancer who were to be treated by combined radiation therapy and chemotherapy were imaged before beginning treatment. They were then followed for up to 3 y for evidence of recurrence or death. Images of the chest, abdomen, and pelvis were obtained 40-90 min after administration of 370-555 MBq (10-15 mCi) (18)F-FDG. Three observers then independently graded the primary tumor for size (0 = small, 1 = moderate, 2 = large), shape (0 = spherical, 1 = nonspherical), heterogeneity of uptake (0 = none, 1 = moderate, 2 = marked), and presence of lymph nodes (0 = none, 1 = pelvic, 2 = paraaortic, 3 = distant). The scores were summed to achieve a total score. A statistical calculation demonstrated that a score cutoff of 4 best separated patients with a good prognosis from patients with a bad prognosis. Kaplan-Meier analysis was used to compute progression-free survival and overall survival. Evaluation of lymph nodes alone was compared with the grading of tumor characteristics. RESULTS: Observers 1 and 2 scored 26 patients as having a good prognosis and 21 as having a bad prognosis. Observer 3 scored 30 and 17, respectively, a statistically insignificant difference. Survival curves were almost identical for the 3 observers. For progression-free survival, approximately 12% of patients with a good score had disease recurrence whereas approximately 75% with a bad score had disease recurrence. For overall survival, approximately 10% (good) and 80% (bad) died. Evaluation of lymph nodes also separated the groups, but not as well as did visual analysis alone. The combination of the 2 was only slightly superior to visual assessment alone. CONCLUSION: A simple, rapid, and highly reproducible system is described for visual grading of characteristics of the primary tumor in patients with cervical cancer at the time of diagnosis. This approach separates patients with a poor prognosis from those who will do well, thus providing a new tool for accurate estimation of prognosis.

PET-guided IMRT for cervical carcinoma with positive para-aortic lymph nodes-a dose-escalation treatment planning study.

PURPOSE: To evaluate a treatment planning method for dose escalation to the para-aortic lymph nodes (PALNs) based on positron emission tomography (PET) with intensity-modulated radiotherapy (IMRT) for cervical cancer patients with PALN involvement. One goal of this process was not to modify the traditional treatment of the pelvic region. METHODS AND MATERIALS: PET images for 4 cervical cancer patents with PALN involvement were registered with their corresponding CT scans. Positive PALNs were identified on PET images, and the surrounding critical structures were delineated on CT images. The treatment machine central axis (CAX) was placed at the level of the L4-L5 vertebral body interspace. There were two distinct treatment regions: the para-aortic bed superior to the CAX and the whole pelvis region inferior to the CAX. IMRT was used for treatment planning of PALN bed irradiation. The positive PALNs identified on PET images were defined as the gross target volume, and the para-aortic bed was defined as the clinical target volume. The radiation doses were escalated from the conventional 45 Gy to 59.4 Gy for the gross target volume and 50.4 Gy for the clinical target volume in 33 fractions. The pelvis area was treated with conventional treatment methods, AP-PA beams to 50.4 Gy in 28 fractions with a brachytherapy implant boost. The placement of the CAX allowed the two treatment regions to be abutted using the treatment machine's independent jaws. RESULTS: Dose escalation to positive PALNs, as identified on PET images, and the PALN bed is feasible with IMRT. Treatment plans for 4 patients revealed that escalated prescription doses could be delivered to target volumes while maintaining acceptable doses to the surrounding critical structures. Strategic placement of the treatment isocenter allows the IMRT region (PALN bed) and whole pelvis fields to be treated with a relatively uniform dose distribution in the abutment region. CONCLUSION: This study indicates that PET-guided IMRT could be used in a clinical trial in an attempt to escalate doses delivered to patients with cervical cancer who have positive PALNs.

Physiologic FDG-PET three-dimensional brachytherapy treatment planning for cervical cancer.

PURPOSE: To compare conventional two-dimensional (2D) orthogonal radiography-based brachytherapy treatment planning for cervical cancer with a three-dimensional (3D) treatment planning technique based on 18F-fluoro-deoxyglucose-positron emission tomography (FDG-PET). METHODS AND MATERIALS: Eleven cervical cancer patients were included in this prospective study that evaluated one tandem and ovoid brachytherapy procedure for each patient. The patient underwent FDG-PET of the pelvis to visualize the tumor followed by a second FDG-PET scan with the FDG isotope placed inside the tandem and ovoid applicators to visualize the treatment source positions for 3D treatment planning. The tumor volumes were delineated using a binary threshold technique in which the threshold FDG-PET image intensity was 40% of the peak tumor intensity. RESULTS: FDG-PET provides a reliable estimate of the cervical cancer volume and 3D spatial relationship of the tumor to the tandem and ovoid applicators. The maximal bladder and rectal doses determined from the 3D FDG-PET dose-volume histograms were found to be higher than those obtained using 2D treatment planning. The minimal dose to the tumor volume defined by FDG-PET ranged from 50 to 475 cGy for treatment plans designed to deliver 650 cGy to Point A and exhibited an inverse correlation with tumor volume. CONCLUSION: Physiologic FDG-PET brachytherapy treatment planning is feasible and accurate relative to conventional 2D treatment planning. The use of FDG-PET offers a unique method for tumor visualization and identifies the limitations of conventional brachytherapy treatment planning for coverage of large tumors and estimation of the dose to normal structures. This technique has the potential for improving isodose tumor coverage for patients with cervical cancer while sparing critical structures.

Measurement of tumor volume by PET to evaluate prognosis in patients with advanced cervical cancer treated by radiation therapy.

PURPOSE: This study evaluated the usefulness of tumor volume measurement with positron emission tomography (PET) in patients with advanced cervical cancer treated by radiation therapy. METHODS AND MATERIALS: Fifty-one patients underwent PET before treatment. Primary tumor volume was determined, and volume, FIGO stage, and presence of lymph nodes on the PET study were compared to progression-free survival (PFS) and overall survival (OS). RESULTS: Tumor volume, lymph node disease, and stage were predictive of PFS, whereas volume and lymph node involvement predicted OS. Lymph node status did not correlate with volume. Dividing patients according to whether the tumor volume was more or less than 60 cm(3) predicted PFS and OS. Separation of patients with tumor volumes

PET-guided three-dimensional treatment planning of intracavitary gynecologic implants.

PURPOSE: Positron emission tomography (PET) provides physiologic information that is not available from computed tomography (CT) or magnetic resonance studies. PET images may allow more accurate delineation of three-dimensional treatment planning target volumes of brachytherapy gynecologic (GYN) implants. This study evaluates the feasibility of using PET as the sole source of target, normal structure, and applicator delineation for intracavitary GYN implant treatment planning. MATERIALS AND METHODS: Standard Fletcher-Suit brachytherapy tandem and colpostat applicators were used for radiation delivery. After insertion of the applicator in the operating room, the patient was taken to a PET scanner, where 555 MBq (15 mCi) 18F-fluorodeoxyglucose (18F-FDG) was administered intravenously. Forty-five minutes later, three localization tubes containing 18F-FDG were inserted into the source afterloading compartments of the tandem and colpostat. A whole-pelvis scan was performed, and the images were transferred to a commercial brachytherapy three-dimensional treatment planning system. A Foley catheter was inserted into the urinary bladder while the patient was in the operating room. The regions of radioactivity in the three applicator tube image were contoured for reconstruction of the applicator, along with the bladder, rectum, and 18F-FDG-defined target volumes. A treatment plan was generated that included dose-volume histograms and three-dimensional dose distribution displays, allowing the physician an opportunity to determine if adequate target coverage and normal-tissue sparing had been obtained. For a more conservative approach, three-dimensional dose distributions and dose-volume histograms delivered with conventional source arrangements and loading could be observed. The accuracy of applicator localization from the PET images was verified using a water phantom containing two aluminum CT-compatible tandems. The PET-defined and CT scan applicator reconstructions were compared. RESULTS: Feasibility of using PET images for treatment planning of brachytherapy intracavitary GYN implants has been demonstrated. A phantom study demonstrated applicator reconstruction accuracy in the axial direction to be better than 2 mm. Reconstruction accuracy in the longitudinal direction (principally craniocaudal) was similar to the PET scanner's voxel size of 4.3 mm. CONCLUSIONS: Brachytherapy intracavitary GYN implant design has traditionally been based on patient tumor staging, palpation, and clinical experience. PET images have the potential to provide better spatial information about the relationship of tumor and normal structures to the applicator. This information can be used to optimize the delivery of radiation therapy treatments. Thus far, six patients have been scanned using this process.

Evaluation of response to neoadjuvant therapy by quantitative 2-deoxy-2-[18F]fluoro-D-glucose with positron emission tomography in patients with esophageal cancer.

PURPOSE: This work evaluates positron emission tomography (PET) with 2-deoxy-2-[18F]fluoro-D-glucose (FDG) in assessing response to therapy in patients with esophageal cancer. PROCEDURES: Twenty-four patients underwent FDG-PET before (pre-Rx) and after (post-Rx) chemoradiation therapy; 20 then underwent esophagectomy. The response of the primary tumors was visually assessed, and tumor volume, peak tumor standardized uptake value (SUV(peak)), average SUV (SUV(ave)), and total lesion glycolysis were determined pre-treatment and post-treatment. Patients were divided into groups according to the absence (Group A) or presence (Group B) of residual tumor after neoadjuvant therapy. RESULTS: Among the quantitative PET parameters for Group A (n = 6) and Group B (n = 18), only change in tumor volume identified complete responders. Quantitative PET indices were not different in patients with or without post-Rx esophagitis. CONCLUSIONS: The change in tumor volume identifies patients with complete response to neoadjuvant therapy, and quantitative evaluation of the primary tumor cannot separate post-Rx inflammation from residual tumor.