Intraoperative high-dose-rate brachytherapy: An American Brachytherapy Society consensus report.

PURPOSE: This report presents recommendations from the American Brachytherapy Society for the use of intraoperative high-dose-rate (IOHDR) brachytherapy. METHODS AND MATERIALS: Members of the American Brachytherapy Society with expertise in IOHDR formulated this document based on their clinical experience and a review of the literature. This report covers the use of IOHDR in colorectal cancer, soft tissue sarcoma, gynecologic cancers, head and neck cancers, and pediatric cancers. This report does not cover intraoperative brachytherapy for breast cancer. Details about treatment planning and delivery are emphasized so this document can serve as a guide to practices implementing this technique. RESULTS: IOHDR brachytherapy is generally most beneficial for patients with either close or positive margins and/or recurrent disease in a previous resection bed or previously irradiated area. IOHDR brachytherapy requires a well-coordinated multidisciplinary team. IOHDR brachytherapy is recommended in the treatment of both recurrent and primary locally advanced disease for colorectal and gynecologic malignancies, soft tissue sarcoma, and selected head and neck and pediatric malignancies. Other techniques such as perioperative fractionated brachytherapy are also acceptable in many cases with some advantages and disadvantages compared to IOHDR. CONCLUSIONS: IOHDR brachytherapy is a specialized technique in radiation therapy with unique properties and advantages in cancer control. Special considerations for treatment planning and delivery are outlined herein.

Changes in gene expression induced by chemoradiation in advanced cervical carcinoma: a microarray study of RTOG C-0128.

PURPOSE: To evaluate gene expression patterns in patients with advanced cervix cancer before and during chemoradiation in a multi-institutional cooperative group setting. METHODS: RTOG C0128 was designed as a Phase II trial of radiation therapy with concomitant chemotherapy and Celecoxib at 400 mg twice daily for one year. Tumor samples were obtained for microarray gene expression analysis before treatment and at the time of the first implant (paired sample). RNA was extracted, linearly amplified, and purity was assessed by gel electrophoresis. Each sample was hybridized against a universal RNA mixture on a customized spotted array consisting of >10,000 genes. Gene expression pre-treatment was compared with clinical characteristics. Changes in gene expression following radiation were assessed within the paired samples (same patient) and then compared across all paired samples. Data were normalized using the AROMA software, and clustering analysis was performed using Ward's method in Spotfire. Differences in paired samples were calculated with Significance Analysis of Microarrays (SAM). RESULTS: From August 2001 to March 2004, 84 patients were accrued to the trial. Tissue was obtained prior to initiation of therapy from 34 patients (40%). FIGO stages of the patients providing tissue were IB (23%), II (57%), and IIIA-IVA (20%). RNA quality was sufficient in 22 pre-treatment and 14 post-treatment samples. Among pre-treatment samples, no significant differences in gene expression were observed by FIGO stage, age, or race. However, between comparison of histologic subtypes (adenocarcinoma, n=5; squamous cell carcinoma, n=17) demonstrated 45 genes differentially expressed with a false discovery rate of 0.018. Cluster analysis segregated unpaired samples into 2 groups: 18/22 comprising pre-treatment samples and 10/14 in group 2 representing post-treatment samples. In all 13 paired samples, gene expression after chemoradiation was significantly upregulated in 91 genes and downregulated in 251 genes (false discovery rate of 0.0018). Genes significantly upregulated included bax, cdk inhibitor 1, MMP2, and adhesion molecules PECAM1, VCAM1, and ICAM2. Genes significantly downregulated included topoisomerase II alpha, myc, H2AX, MSH2, RAD51, RAD53, PCNA, and cell cycle-regulating molecules chk1, CDK2, cyclinB1, cyclin D3, cdc2, and cdc25. CONCLUSIONS: Microarray analysis was successfully performed in a multi-institutional cooperative group trial. Gene expression significantly correlated with histology, but not stage, age or race. Cluster analysis identified two groups of gene expression profiles correlating with pre or post-treatment acquisition of tissue. Notably, paired samples showed significant changes in gene expression following chemoradiation, including several downregulated radiation response genes. Further analysis comparing gene expression to clinical outcomes, acute and late toxicities awaits maturation of clinical data. Hopefully, this data will lead to the development of molecularly based therapies.

Survival impact of lymph node dissection in endometrial adenocarcinoma: a surveillance, epidemiology, and end results analysis.

The therapeutic benefit of lymph node dissection (LND) in women with endometrial cancer remains controversial. The purpose of this study is to analyze the impact of LND on survival. Data were obtained from the Surveillance, Epidemiology, and End Results program of the US National Cancer Institute for the years 1988-2003. Women with adenocarcinoma of the endometrium who underwent surgery as primary management of their disease were eligible. Multivariate analyses of pertinent variables were performed for the end points of overall survival and cause-specific survival. Women included in the analysis were 42,184. The average frequency of LND was 31%, 40%, 47%, and 53%, for the years 1988-1991, 1992-1995, 1996-1999, and 2000-2003, respectively (P < 0.0001). On multivariate analysis, presence of LND was associated with overall and uterine-specific survival benefits with hazard ratios (HR) of 0.81 (P < 0.0001) and 0.78 (P < 0.0001) and removal of greater than 11 lymph nodes (LN) associated with a HR of 0.74 (P < 0.0001) and 0.69 (P < 0.0001), respectively. Further multivariate analyses demonstrated greater than 11 LN to associate with all other cause-specific and cardiac-specific survival benefits, with HR of 0.77 (P < 0.0001) and 0.82 (P = 0.0062), respectively. We conclude that the presence of LND and increased number of nodes dissected predicted for improved overall and uterine-specific survival in women with adenocarcinoma of the endometrium. Improved cause-specific survival was most pronounced for greater than 11 nodes removed and stage II or higher disease. The improvement in noncancer-related mortality with LND predicted by this data suggests the presence of inherit biases, and the need for caution in analyzing retrospective data.

Feasibility of RNA collection for micro-array gene expression analysis in the treatment of cervical carcinoma: a scientific correlate of RTOG C-0128.

PURPOSE: To determine the feasibility of RNA collection in a multi-institutional cooperative group setting to be utilized for micro-array gene expression analysis, and to describe the methodology. METHODS: RTOG C0128, a phase I-II, protocol was designed to look at the safety and efficacy of external beam radiation therapy to 45 Gy with concomitant 5-FU and cisplatin chemotherapy, brachytherapy to deliver 85 Gy to point A, and Celecoxib at 400 mg twice daily for 1 year. Patients had the option of participating in a tissue collection portion of the protocol to be utilized for micro-array gene expression analysis before treatment and at the time of the first implant. RNA quality was determined by two parameters: the absorbance ratio at 260 nm/280 nm, and by the ratio of the integrated peak of 28S RNA to 18S RNA after gel electrophoresis. RESULTS: From August 2001 to March 2004, 84 patients were accrued to the trial, and tissue was obtained prior to initiation of therapy on 34 patients (40%). FIGO stages for the patients who provided tissue were IB (23%), II (57%), and IIIA-IVA (20%). Additionally, biopsies were obtained at the time of the first implant from 22 of the accrued patients making paired samples available on 26% for RNA extraction and micro-array gene expression analysis. The mean +/- SEM amount of tissue obtained pretreatment was 97 +/- 13 mg compared with 51 +/- 8 mg for tissue obtained at the time of the first implant (P = 0.009). The mean total RNA extracted from the samples prior to treatment was 119 +/- 19 microg versus 35 +/- 6 microg at the time of the first procedure (P = 0.001). The RNA quality was assessed via the absorbance ratio at 260 nm divided by 280 nm. The mean values pretreatment and at first implant were 1.87 +/- 0.07 versus 1.66 +/- 0.11, respectively (P = 0.002); however, the integrated peak of 28S RNA to 18S RNA after gel electrophoresis was not significantly different (P = 0.26). CONCLUSIONS: RNA extraction for gene expression analysis can be successfully performed in the multi-institutional cooperative group setting. Fresh tissue samples were obtained on 40% of accrued patients prior to treatment. The amount of biopsy material and the quantity of RNA extracted were greater prior to treatment compared with the first implant. The quality of RNA was superior prior to treatment as measured by the ratio of absorbance at 260/280 nm. These results indicate that gene expression analysis is feasible in the cooperative group setting utilizing amplification techniques for the RNA. Hopefully, this will allow for improvement in prognosis, therapeutic development, and correlation with acute and late toxicities in patients with cancer.

Electron arc irradiation of the postmastectomy chest wall with CT treatment planning: 20-year experience.

PURPOSE: Since 1980, electron arc irradiation of the postmastectomy chest wall has been the preferred radiotherapy technique at the University of Utah for patients with advanced breast cancer. We report the results of this technique in 156 consecutive Stage IIA-IIIB patients treated from 1980 to 1998. METHODS: CT treatment planning was used in all patients to identify chest wall thickness and internal mammary lymph node depth. Computerized dosimetry was used to deliver total doses of 50 Gy in 5-1/2 weeks to the chest wall and the internal mammary lymph nodes with electron arc therapy. Patients were assessed for local, regional, and distant control of disease and for survival. Univariate and multivariate proportional hazards were modeled using a hierarchical nonproportional semiparametric model testing the following prognostic factors: age, stage, tumor size, number of positive lymph nodes, estrogen receptor status, and dose. End points evaluated included disease-free survival, cause-specific survival, and overall survival. RESULTS: Eighty-one percent of patients were at high risk for local-regional failure because of > T2 primary tumor or > 3 positive axillary lymph nodes. The median number of positive lymph nodes was 5, and the median tumor size was 3.5 cm. Actuarial 10-year local-regional control and overall survival were 95% and 52%, respectively. In multivariate analysis, the only factor prognostic for disease-free survival, cause-specific survival, and overall survival was the number of positive lymph nodes (p < 0.001). The 10-year rates of local-regional control for patients with 0, 1-3, 4-9, and > or = 10 involved lymph nodes were 100%, 98%, 93%, and 89%, respectively. The only rates of acute and chronic radiotherapy toxicity > or = 2 by RTOG/EORTC criteria were skin related and observed in 44% and 10% for acute and late reactions, respectively. CONCLUSION: These data demonstrate excellent local-regional control rates with electron arc therapy of the postmastectomy chest wall in patients with advanced breast cancer. Our 20-year experience with electron arc radiotherapy has demonstrated the safety and efficacy of this technique. The advantage of this technique is that the internal mammary lymph node chain can be easily encompassed while the dose to heart and lung is minimized; it also obviates match lines in areas of high risk.

Elevated COX-2 expression in cervical carcinoma: reduced cause-specific survival and pelvic control.

The purpose of this study was to correlate the level of cyclooxygenase-2 (COX-2) expression in carcinoma of the cervix with the clinical endpoints: local control, cause-specific survival, and patterns of failure in patients treated with radiotherapy. Formalin-fixed, paraffin-embedded tumor biopsies were stained for COX-2. Clinical factors such as stage, grade, tumor size, pre- and posttreatment hemoglobin level, and radiotherapy dose were also evaluated. Actuarial local control rates and cause-specific survival were determined according to the Kaplan-Meier method. COX-2 distribution staining was the only prognostic factor that was associated with local control and cause-specific survival. High COX-2 distribution staining was associated with decreased local control and decreased cause-specific survival by log rank comparison of Kaplan-Meier survival curves. The 5-year cause-specific survival rates for tumors with low versus high COX-2 distribution values were 90% and 22%, respectively (p = 0.0003). Actuarial pelvic control at 5 years was superior in patients with low COX-2 distribution staining (92%) compared with high staining (42%, p = 0.005). COX-2 staining intensity was found to correlate positively with tumor size (p = 0.02). These findings indicate that increased expression of COX-2 yields reduced pelvic control and cause-specific survival in patients with invasive carcinoma of the cervix treated with radiotherapy. Previously, inhibition of COX-2 has been demonstrated to sensitize tumors to radiation without effect on normal tissue. Taken together, these data may support a novel therapeutic application of COX-2 inhibitors in the treatment of carcinoma of the cervix.

Intensity-modulated radiosurgery/radiotherapy using a micromultileaf collimator.

Intensity modulation with inverse treatment planning for 3 clinical stereotactic radiotherapy cases were directly compared against forward planning techniques using beam modification by enhanced dynamic wedge. Dose-volume histogram (DVH) analysis demonstrated that a significant reduction in dose to neighboring critical structures can-be achieved through intensity modulation patterns determined from inverse planning, while a marginal change is achieved in the target volume dose uniformity. This study also demonstrates that the intensity modulated dose patterns generated from inverse planning may differ significantly from the intuitive beam modified patterns developed in the forward planning model. These results suggest that one advantage of intensity modulated radiosurgery/radiotherapy with inverse planning is the significant reduction in dose to normal tissue and critical structures, with its coincident implications for dose escalation studies.

Elevated cyclooxygenase-2 expression correlates with diminished survival in carcinoma of the cervix treated with radiotherapy.

PURPOSE: The purpose of this study was to examine the relationship between overall survival and prognostic factors in carcinoma of the cervix treated with radiation therapy. A clinicopathologic study was performed on 24 patients. METHODS AND MATERIALS: Formalin-fixed, paraffin-embedded tumor biopsies were stained for Cyclooxygenase-2 (COX-2), Topoisomerase I, Topoisomerase II, and p53. Clinical factors such as stage, grade, tumor size, pre- and post-treatment hemoglobin level, and radiotherapy dose were also evaluated. RESULTS: Median follow-up was 75 months for living patients. The only immunohistochemical or clinical factor that was associated with improved survival was decreased COX-2 distribution staining. High COX-2 distribution staining was associated with decreased overall survival (p = 0.021) and decreased disease-free survival (p = 0.015) by log-rank comparison of Kaplan-Meier survival curves. The 5-year overall survival rates for tumors with low vs. high COX-2 distribution values were 75% and 35%, respectively. COX-2 staining intensity was found to correlate positively with tumor size (p = 0.022). CONCLUSION: These findings indicate that increased expression of COX-2 portends a diminished survival in patients with invasive carcinoma of the cervix treated with radiotherapy. Because COX-2 is an early-response gene involved in angiogenesis and inducible by different stimuli, these data may indicate opportunity to intervene with specific inhibitors of COX-2 in carcinoma of the cervix.

Breast cancer after mantle irradiation for Hodgkin's disease: correlation of clinical, pathologic, and molecular features including loss of heterozygosity at BRCA1 and BRCA2.

PURPOSE: Hodgkin's disease patients who receive mantle irradiation have an age-dependent increased risk of developing breast cancer. To determine if genetic factors predispose these patients to develop breast cancer, we evaluated breast cancer specimens for loss of heterozygosity (LOH) at regions where BRCA1 and BRCA2, two breast cancer tumor suppressor genes, are located. We also evaluated whether breast cancers in patients who were previously treated with radiation have a more aggressive phenotype, and whether the clinical course differed from a sporadic group of breast cancer patients. METHODS AND MATERIALS: All females with Hodgkin's disease who were subsequently diagnosed with breast cancer and for whom tissue blocks were available were included. Using a case-control design, case patients (previously treated with radiation therapy) were matched with sporadic control breast cancer patients for age, breast cancer stage, and date of breast cancer diagnosis. After microdissection of tumor and normal tissue from paraffin-embedded tissue blocks, DNA was extracted and samples were examined for LOH at chromosomal segments encompassing BRCA1 and BRCA2. Breast cancer specimens were also evaluated in a blinded fashion for tumor grade and immunoreactivity to estrogen and progesterone receptors, p53, her2-neu, and topoisomerase II alpha. Comparisons were made between the case and control populations using chi2 analysis, and a paired Student's t test. Survival differences were evaluated using a log-rank test. RESULTS: From January 1960 to December 1983, 917 patients were diagnosed with Hodgkin's disease. Twelve patients were subsequently diagnosed with breast cancer and tissue blocks were available on 10 cases. No statistical difference was observed between the case and control populations for LOH at BRCA1 or BRCA2. In the Hodgkin's disease group, LOH was observed in 30% of tumors at BRCA1 and 10% of tumors at BRCA2 vs. 10% and 0% of tumors in the control group at BRCA1 and BRCA2, respectively. Breast tumors from patients who received radiation therapy for Hodgkin's disease displayed greater nuclear pleomorphism (p < 0.02), and an increase in topoisomerase II alpha expression (p < 0.05) vs. the control population. Five of 10 patients were pregnant at the time of their Hodgkin's treatment, and those patients had a shorter time interval to the development of breast cancer compared with the patients who were not pregnant (12.4 years compared with 18.6 years). There was no significant difference in disease-free survival; however, overall survival was inferior in the population previously treated with radiation therapy for Hodgkin's disease (p = 0.01). 80% of patients with a previous Hodgkin's diagnosis died of breast cancer or treatment related effects vs. 30% in the control group. CONCLUSION: We were unable to find statistical evidence for LOH at BRCA1 and BRCA2 in breast cancers from patients previously irradiated for Hodgkin's disease. Breast cancer diagnosed after mantle irradiation may be more biologically aggressive based on the greater nuclear pleomorphism and increase in topoisomerase II alpha staining. This did not translate into a statistical difference in breast cancer disease-free survival; however, overall survival was significantly inferior in the Hodgkin's disease patients.

Effects of modifying topoisomerase II levels on cellular recovery from radiation damage.

Effects of Modifying Topoisomerase II Levels on Cellular Recovery from Radiation Damage. Experiments were performed with the budding yeast, Saccharomyces cerevisiae, to test whether DNA topoisomerase II is involved in repair of DNA damage induced by ionizing radiation. Topoisomerase II was inactivated by use of a temperature-sensitive mutation. Enzyme inactivation increased cellular radiosensitivity, blocked the restitution of broken chromosomes, assayed by pulsed-field gel electrophoresis, and prolonged the induction of a DNA damage-inducible gene (RNR3). Overexpression of the topoisomerase II gene did not alter cellular radiosensitivity. The data support a role for topoisomerase II in the repair of DNA strand breaks.

Application of enhanced dynamic wedge to stereotactic radiotherapy.

Stereotactic radiotherapy has developed into a useful treatment technique in which conformal dose distributions can be delivered with precision and accuracy. In some cases, the position of the target volume relative to surrounding critical structures demands careful evaluation of fixed beam paths so that dose to these critical structures can be minimized. Micromultileaf collimators aid in conforming dose to the target volume but may not allow adjustment of an individual beam's intensity (intensity modulation) in an effort to achieve dose uniformity throughout the treatment volume. Enhanced dynamic wedge (EDW) is demonstrated to be a valuable tool in improving the dose distribution in stereotactic radiotherapy treatments in which these fixed, conformal fields must be used due to constraints in beam trajectories. Four cases are presented which show the potential for gain in dose uniformity with the addition of EDW. These cases represent typical applications of EDW to conformal stereotactic radiotherapy.

Elevations of DNA topoisomerase I in transitional cell carcinoma of the urinary bladder: correlation with DNA topoisomerase II-alpha and p53 expression.

DNA topoisomerase I (topo I) is the molecular target of the camptothecin group of antitumor drugs. Laboratory studies have indicated that cells sensitive to these drugs contain elevated levels of topo I. In this study, we immunostained 49 cases of transitional cell carcinoma from the urinary bladder with a monoclonal antibody directed against human topo I. We found elevated expression of the enzyme in 77% (38 of 49). This included three of six grade I tumors (50%), 9 of 15 grade II tumors (60%), 14 of 15 grade III tumors (93%) and 12 of 13 grade IV tumors (92%). Because the number of cycling cells in a tumor also may be an important determinant of topo I drug response, a proliferation index (topo II-alpha) also was performed for each case. The average topo II-alpha index of grade I tumors was 7.5 x 3.8; for grade II tumors, 20.1+/-10.5; for grade III tumors, 40.3 x 8.2; and for grade IV tumors, 50.5+/-13.0. Because a functional p53 tumor suppressor gene may be necessary for anticancer drug response, we also evaluated our cases for alteration in p53 function. Mutations in the p53 tumor suppressor gene, estimated by immunohistochemical staining, were common, occurring in 23 of 49 cases (47%). The number of cases with elevated topo I, a large growth fraction, and a functional p53 tumor suppressor gene was 4 of 49 (8%). Our results suggest that a small population of patients with transitional cell carcinoma of the urinary bladder may have tumors with molecular features suggesting responsiveness to the new anticancer drugs targeting topo I.

Pathobiologic characteristics of hereditary breast cancer.

Patients with hereditary breast cancer (HBC) present at a young age with breast cancers that show adverse pathological characteristics such as high nuclear grade, negative hormone receptor status, and high proliferation indices. Surprisingly, the clinical course has been reported to be comparable or improved compared with patients with nonhereditary breast cancer (non-HBC). To determine whether there are any molecular markers that might help explain this paradox between pathologically aggressive neoplasms in patients with HBC and the lack of extreme clinically aggressive disease, we studied several molecular parameters in a group of 34 breast cancer patients with mutations in either the BRCA1 or BRCA2 tumor suppressor genes and compared them with a group of 20 breast cancer patients with non-HBC. In general, patients with HBC had tumors that were of higher nuclear grade, contained a higher population of proliferating cells, showed increased expression of DNA topoisomerase II-alpha (topo II-alpha), lacked hormone receptors, and were more likely to show immunopositivity for the p53 tumor suppressor gene. Additionally, tumors from patients with HBC showed a decreased angiogenesis compared with controls. The decreased angiogenesis and the elevated expression of topo II-alpha (an anticancer drug target) may, in part, explain the lack of correlation between clinical course and histological characteristics in patients with HBC.

Response to radiation therapy and prognosis in breast cancer patients with BRCA1 and BRCA2 mutations.

BACKGROUND AND PURPOSE: The purpose of this study is to evaluate overall survival in BRCA1 or BRCA2 breast cancer patients, describe presenting stage, review histologic findings and evaluate response to radiotherapy. MATERIALS AND METHODS: A retrospective study was performed evaluating breast cancer patients with known mutations of BRCA1 or BRCA2. Patients from 12 different pedigrees were cross-referenced with the Utah Cancer Registry (UCR), histologic findings were verified and radiotherapy records were reviewed for acute response to treatment. Actuarial survival calculations were performed and patients were matched for age, date of diagnosis and tumor size. RESULTS: Thirty breast cancer patients with BRCA1 mutations were found to have 34 breast cancers (four had bilateral metachronous lesions) and 20 breast cancer patients with BRCA2 mutations were found to have 22 breast cancers (two had bilateral metachronous disease). The median age at diagnosis was 49 years (range 21-77 years) and 42 years (range 23-83 years), respectively, for BRCA1 and BRCA2 patients. Unusual histologic types of breast cancers were represented with 7% (4/56) medullary and 5% (3/56) lobular carcinomas. Complete staging was possible for 63% (35/56) of cancers. Stages I, II, III and IV represented 26, 63, 6 and 6% of cancers, respectively. The most severe radiation reaction was moist desquamation which was self-limiting and developed in 29% (6/21) of irradiated patients. The mean follow-up was 9.8 and 7.5 years for BRCA1 and BRCA2 cancers, respectively. Kaplan-Meier survival analysis demonstrated 5-year survival values of 75% for BRCA1 patients, 73% for BRCA2 patients, 70% for matched controls and 69% for UCR controls. No statistically significant differences were evident between the groups at 5 or 10 years. CONCLUSIONS: Despite their younger age at presentation, breast cancer patients harboring BRCAI or BRCA2 mutations present at a similar stage, display a normal acute reaction to radiotherapy and have a similar prognosis when compared with sporadic breast cancer patients.

Dosimetric parameters of enhanced dynamic wedge for treatment planning and verification.

Treatment planning for Enhanced Dynamic Wedge requires a knowledge of the dosimetric parameters of the treatment fields. These dosimetric parameters include depth doses, surface doses, buildup doses, peripheral doses, beam profiles, wedge angles and wedge factors. These parameters and their application to treatment planning are evaluated and compared with standard open field and metal wedge field dosimetric parameters.

Dose to the contralateral breast: a comparison of two techniques using the enhanced dynamic wedge versus a standard wedge.

The dose to the contralateral breast has been associated with an increased risk of developing a second breast malignancy. Varying techniques have been devised and described in the literature to minimize this dose. Metal beam modifiers such as standard wedges are used to improve the dose distribution in the treated breast, but unfortunately introduce an increased scatter dose outside the treatment field, in particular to the contralateral breast. The enhanced dynamic wedge is a means of remote wedging created by independently moving one collimator jaw through the treatment field during dose delivery. This study is an analysis of differing doses to the contralateral breast using two common clinical set-up techniques with the enhanced dynamic wedge versus the standard metal wedge. A tissue equivalent block (solid water), modeled to represent a typical breast outline, was designed as an insert in a Rando phantom to simulate a standard patient being treated for breast conservation. Tissue equivalent material was then used to complete the natural contour of the breast and to reproduce appropriate build-up and internal scatter. Thermoluminescent dosimeter (TLD) rods were placed at predetermined distances from the geometric beam's edge to measure the dose to the contralateral breast. A total of 35 locations were used with five TLDs in each location to verify the accuracy of the measured dose. The radiation techniques used were an isocentric set-up with co-planar, non divergent posterior borders and an isocentric set-up with a half beam block technique utilizing the asymmetric collimator jaw. Each technique used compensating wedges to optimize the dose distribution. A comparison of the dose to the contralateral breast was then made with the enhanced dynamic wedge vs. the standard metal wedge. The measurements revealed a significant reduction in the contralateral breast dose with the enhanced dynamic wedge compared to the standard metal wedge in both set-up techniques. The dose was measured at varying distances from the geometric field edge, ranging from 2 to 8 cm. The average dose with the enhanced dynamic wedge was 2.7-2.8%. The average dose with the standard wedge was 4.0-4.7%. Thermoluminescent dosimeter measurements suggest an increase in both scattered electrons and photons with metal wedges. The enhanced dynamic wedge is a practical clinical advance which improves the dose distribution in patients undergoing breast conservation while at the same time minimizing dose to the contralateral breast, thereby reducing the potential carcinogenic effects.

Electron arc irradiation of the postmastectomy chest wall: clinical results.

BACKGROUND AND PURPOSE: Since 1980 electron arc irradiation of the postmastectomy chest wall has been the preferred technique for patients with advanced breast cancer at our institution. Here we report the results of this technique in 140 consecutive patients treated from 1980 to 1993. MATERIALS AND METHODS: Thoracic computerized tomography was used to determine internal mammary lymph node depth and chest wall thickness, and for computerized dosimetry calculations. Total doses of 45-50 Gy in 5 to 5 1/2 weeks were delivered to the chest wall and internal mammary lymph nodes via electron arc and, in most cases, supraclavicular and axillary nodes were treated with a matching photon field. Patients were assessed for acute and late radiation changes, local and distant control of disease, and survival. Patients had a minimum follow-up of 1 year after completion of radiation treatment, and a mean follow up interval of 49 months and a median of 33 months. All patients had advanced disease: T stages 1, 2, 3, and 4 represented 21%, 39%, 21% and 19% of the study population, with a mean number of positive axillary lymph nodes of 6.5 (range, 0-29). Analysis was performed according to adjuvant status (no residual disease, n = 90), residual disease (positive margin, n = 15, and primary radiation, n = 2), or recurrent disease (n = 33). RESULTS: Acute radiation reactions were generally mild and self limiting. A total of 26% of patients developed moist desquamation, and 32% had brisk erythema. Actuarial 5 year local-regional control, freedom from distant failure, and cause-specific survival was 91%, 64%, and 75% in the adjuvant group; 84%, 50%, and 53% in the residual disease group; and 63%, 34%, and 32% in the recurrent disease group, respectively. In univariate Cox regressions, the number of positive lymph nodes was predictive for local failure in the adjuvant group (P = 0.037). Chronic complications were minimal with 11% of patients having arm edema, 17% hyperpigmentation, and 13% telangectasia formation. CONCLUSION: These data demonstrate that local-regional control with electron are therapy of the postmastectomy chest wall is comparable to photon techniques. Acute radiation reactions are well tolerated and mostly of minor extent. A previous report demonstrated a significant reduction in the dose-volume relationship of the lung using the electron arc compared with two photon techniques. Consequently, with careful attention to treatment planning and dosimetry, electron arc therapy of the postmastectomy chest wall is safe and effective. The radiation dose to heart and lung is minimized without compromise on local control.

Iododeoxyuridine radiosensitization of human glioblastoma cells exposed to acute and chronic gamma irradiation: mechanistic implications and clinical relevance.

PURPOSE: Iododeoxyuridine (IdUrd) is a recognized sensitizer of sparsely and some densely ionizing radiations. The mechanism of sensitization remains uncertain. Sensitization is likely to involve increased production of DNA damage and/or inhibition of DNA damage repair. To test these possibilities, we have characterized acute and chronic radiosensitization, and the sublethal damage repair capacity of two human glioblastoma cell lines, with or without clinically relevant concentrations of IdUrd. MATERIALS AND METHODS: Exponentially growing human glioblastoma cell lines, G18 and U251, were irradiated with acute (1.4 Gy/min) and chronic (20, 40, and 80 cGy/hr) cobalt 60 exposures in the presence and absence of 0 to 10 microM IdUrd. Clonogenic survival was determined. Sensitizer enhancement ratios and global survival curve comparisons were determined with and without IdUrd. Repair half-times for chronic exposures with and without IdUrd were calculated. Split-dose recovery following acute fractions of 5 Gy separated by 0, 0.5, 1, 2, and 5 hours was evaluated. RESULTS: Following acute exposure, a sensitizer enhancement ratio at 10% survival of 1.85 and 1.75 was observed at concentrations of 10 microM IdUrd for the G18 and U251 cell lines, respectively. A global comparison of the survival curves similarly revealed significant sensitization at 10 microM IdUrd. Sensitizer enhancement ratios and global comparisons of the chronic exposures showed significant sensitization in the presence of 2 microM IdUrd for both lines. No significant interaction between dose rate and IdUrd effect could be shown using a global comparison. Repair half-times for chronic exposures were similar in the presence or absence of IdUrd. Both cell lines demonstrate capacity for sublethal damage repair in the presence of 2 microM IdUrd in split-dose experiments. CONCLUSION: The results of the chronic clonogenic and split-dose studies suggest that increased DNA damage production contributes to the mechanism of IdUrd radio-sensitization, perhaps more so than repair inhibition. A capacity for sublethal damage repair is not necessarily a prerequisite for sensitization. IdUrd remains an attractive sensitizer of ionizing irradiation delivered at high or low dose rates, particularly for actively growing tumors located in quiescent normal tissues.