We used a computer tomography (CT)-assisted three-dimensional (3D) technique to assess dose to the rectum and bladder in intracavitary brachytherapy (ICBT) for patients with cervical cancer, and compared this technique with the conventional method. The results revealed that the difference in dose to the rectal and bladder wall between these two methods were significant. The CT-assisted technique is a feasible method, and it gives different results than the conventional method.

PURPOSE:To measure the degree of attenuation of radiation dose by the skull base bone in patients with nasopharyngeal carcinoma (NPC) and to study its clinical importance.MATERIALS AND METHODS:Isodose distribution in 11 patients with NPC who received bilaterally opposed large-field irradiation (1.8 Gy per fraction) was studied with a three-dimensional treatment planning system with tissue inhomogeneity correction. Also studied were the sites of local tumor recurrence in 37 patients with NPC and skull base destruction (>/=0.5 cm) or intracranial invasion treated with radiation therapy from January 1989 to December 1992. Regression analyses were performed.RESULTS:In the dosimetric study, the low-dose areas (<1.65 Gy) were located at the level of the skull base in all 11 patients. A significantly positive correlation between the maximum width of the skull base bone and the low-dose volume (<1.65 Gy) was demonstrated (P =.003, linear regression). In the clinical study, local tumor recurrence was noted in 18 patients (49%). The sites of local recurrence included skull base in 16 patients (43%) and nasopharynx in six patients (16%). Wider skull base bone was a significant predictor of skull base recurrence after radiation therapy (P =.03, logistic regression).CONCLUSION:Herein demonstrated is the inadequacy of the radiation dose over the skull base due to attenuation by the skull base bone. The relationship between width of skull base bone and skull base tumor recurrence also is established.

PURPOSE:To quantitatively investigate the clinical implications of tumor regression rate (TRR-45) and nodal regression rate (NRR-45) of nasopharyngeal carcinomas (NPC) after receiving 45 Gy of radiotherapy (RT). The values, predictive values, and associated factors of TRR-45 and NRR-45 in NPC are analyzed. METHODS AND MATERIALS:One hundred one patients with newly diagnosed NPC and who were curatively treated by RT alone were included in the study. Tumor volume and nodal volume before treatment and after 45 Gy were obtained from computed tomographic (CT) scans performed at those times and calculated with the assistance of a computer-based imaging analyzing system. TRR-45 (NRR-45) was defined as the ratio of reduced tumor (nodal) volume after 45 Gy to the initial tumor (nodal) volume. TRR-45 (NRR-45) values were stratified into three groups of slow (below 50%), moderate (between 50% and 75%), and rapid (above 75%) change. After conventional RT with 45 Gy, conformal RT for primary tumors was boosted to 70.2-72 Gy for T1-2 tumors, and 75.6-81 Gy for T3-T4 tumors. RT for residual neck masses was boosted by electron beam to 61-75 Gy. RESULTS:The mean value of TRR-45 for all patients was lower than that of NRR-45 for the 78 patients with metastatic neck nodes (70% +/- 4.8% vs. 81% +/- 5%, p = 0.003). The 3-year actuarial neck control rate was better than the primary tumor control rate with statistical significance (98% vs. 85%, p = 0.009). No significant statistical differences concerning local control probability, nodal control probability, or survival rate were found among patients with slow, moderate, or rapid TRR-45 or NRR-45. T-stage was the only significant prognostic factor for locoregional control after multivariate analysis. Tumor volume and T-stage were found to have a statistically significant negative correlation with TRR-45. No associated factor was found to be significantly correlated with NRR-45. CONCLUSION:Slow regression rates of the primary tumor or neck nodes in NPC after receiving 45 Gy of irradiation do not mean ultimately poor radiocurability, but may merely imply slow clearance of the cells damaged during irradiation. The different radiobiological behaviors of the regression rates during treatment, ultimate control probabilities, or associated factors for regression rates of NPC between primary tumors and neck nodes need to be further investigated.

Background and purpose: To evaluate the factors associated with pulmonary fibrosis after postmastectomy electron beam irradiation of chest wall and regional lymphatics in patients with breast cancer.Materials and methods: From July 1987 through July 1994, 109 women with stage II and III breast cancer receiving modified radical mastectomies were managed by postoperative electron beam irradiation. Doses of 46 to 50.4 Gy were delivered to the chest wall covered with bolus, internal mammary nodes, supraclavicular nodes and axillary lymph nodes via 12 or 15 MeV single portal electron beam. Seventeen patients received additional 10-16 Gy surgical scar boost via 9 MeV electron beam. Comparison of pre-treatment and post-treatment chest X-ray films were used to monitor the development of pulmonary fibrosis.Results: Only Grade 1 radiation-induced late pulmonary toxicity was noted in 33 patients (29%). Twenty-six patients (24%) developed pulmonary fibrosis under unbolused chest wall. Lung fibrosis under bolused chest wall was noted in 11 patients (10%). Statistical difference (P < 0.01) was noted between the incidence of fibrosis in these two sites. In multivariate analysis of lung fibrosis under unbolus-covered chest wall, the independent prognostic factors, are low body mass index (BMI) (P < 0.01), tamoxifen taking (P = 0.03), and no treatment interruption (P = 0.03). No independent factor was associated with lung fibrosis under bolus-covered chest wall in multivariate analysis.Conclusions: In the analysis of pulmonary fibrosis induced by unbolused electron beam, BMI rather than body weight and body height is a strong prognostic factor. Tamoxifen and short overall time can predispose the development of lung fibrosis. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.

Purpose: To report the treatment results and rectal/bladder complications of cervical carcinoma radically treated with high-dose-rate intracavitary brachytherapy (HDR-IC). The current policy of using three-fraction scheme was examined.Methods and Materials: Between November 1987 and August 1990, 173 patients with cervical carcinoma were treated with curative-intent radiation therapy. Whole pelvic irradiation was administered with 10-MV X ray. Dose to the central cervix was 40-44 Gy in 20-22 fractions, following by pelvic wall boost 6-14 Gy in three to seven fractions with central shielding. Co-60 sources were used for HDR-IC, and 7.2 Gy was given to Point A for three applications, 1-2 weeks apart. Duration of follow-up was 5-7.8 years.Results: Twenty-eight patients (16%) developed central-regional recurrences. Overall 5-year actuarial pelvic control rate was 83%. By stage, 5-year actuarial pelvic control rates were 94%, 87%, and 72% for Stages IB + IIA, IIB + IIIA, and IIIB + IVA, respectively. Thirty-one patients (18%) developed distant metastasis. Overall 5-year actuarial survival rate was 58%. By stage, 5-year actuarial survival rates were 79%, 59%, and 41% for Stages IB + IIA, IIB + IIIA, and IIIB + IVA, respectively. Sixty-six (38%) and 19 patients (11%) developed rectal and bladder complications, respectively. For rectal complication, the overall actuarial rate was 38% at 5 years. By grade, 5-year actuarial rectal complication rates were 24%, 15%, 4%, and 3% for Grades 1-4, respectively. Overall prevalence of rectal complications was 37% and 14% at 2 and 5 years, respectively. Prevalence of low-grade rectal complication (Grades 1 and 2) was dominant at 2 years (30%), but declined to 8% at 5 years. Prevalence of high-grade, severe rectal complication (Grades 3 and 4) remained steady at 2 and 5 years (7% and 6%, respectively). Five-year actuarial bladder complication was 9%. Five-year prevalence of bladder complication was 2%.Conclusion: Using a three-fraction scheme, survival rate appeared comparable with the existing results of the low-desk-rate technique. The incidence of rectal complication with this scheme remained relatively high. The increased part of rectal complication was predominately low grade. This result suggested that therapeutic gain with this scheme may not be good enough to circumvent its biologic disadvantage. Numbers of fractions >3 must be considered in future trials. (C) 1997 Elsevier Science Inc.

Purpose: A technique for whole-body electron therapy with the patient in a lying position has been developed, This technique allows Total Skin Electron Therapy (TSET) for those patients who were previously unable to be treated in a conventional standing position.Methods and Materials: This study was carried out on a Varian 2100C linear accelerator with a 6 MeV high dose rate electron beam. The collimator was open to a width of 36 x 36 cm, There were two main procedures, with six dual-field techniques: 1) two static AP/PA vertical dual fields (VDF): the patient laid on the floor transversely under the collimator when the gantry was in a vertical position, A 0.6 cm acrylic board was placed 15 cm away from the patient, then the gantry was rotated 25 degrees clockwise end counterclockwise to treat the patient in the supine and prone positions, respectively, 2) Four oblique junction fields (OJF): the patient laid on the floor in a prone and supine position parallel to the wave guide at (227 - body thickness X tan 60 degrees) cm away from the vertical axis of the gantry, then the gantry was rotated 60 degrees toward the patient, A 0.6 cm acrylic board was placed 15 cm away from the patient perpendicular to the beam, The patient was move along the field central axis, It allowed the patient's body to be within the 160 cm effective treatment profile, When the patient's body axis move 5 degrees toward the lateral side of the field central axis, we could obtain a better dose distribution in the vertex of the scalp and the soles of the feet, The angle of the VDF was measured by chamber detectors to obtain the effective treatment profile, Likewise, the optimal profile for the OJF was determined by the same procedures, The Rando phantom was used to measure the superficial dose of the body.Results: The dimension of effective treatment profile for the VDF was 188 x 72 cm at 87% dose level, For the OJF, we had to move the patient along the held central axis to obtain the effective treatment profile in a 180 x 85 cm dimension at a 87% dose level, The vertex and sole dose measured in this setup was in the range of 80-88%.Conclusions: The empirical data showed that the lying-on position for TSET was technically feasible. The dose distribution in the body surface was also compatible with the Stanford standing technique, The nonambulatory skin malignancy patient can be treated in a comfortable and reproducible position. (C) 1997 Elsevier Science Inc.