Dose Gradient Index for Stereotactic Radiosurgery/Radiation Therapy.

PURPOSE: Steep dose falloff outside of tumors is a hallmark of stereotactic radiosurgery (SRS) and radiation therapy (SRT). Dose gradient index (DGI) quantifies the dose drop off. Tables of DGIs versus target volumes have been published for body sites, but none is available for brain. This study recommends guidelines for DGIs for brain SRS/SRT treatments based on clinical CyberKnife (CK) cases. METHODS AND MATERIALS: Four hundred ninety-five plans for patients with central nervous system tumors treated with CK at our institution between March 2015 and May 2018 were analyzed. The CK treatment planning system MultiPlan was used for planning. SRS/SRT plans were stratified into 6 groups by tumor size (Group I [0-1 cm3], II [1.0-3.0 cm3], III [3.0-5.0 cm3], IV [5.0-10.0 cm3], V [10.0-15.0 cm3], and VI [15.0-40.0 cm3]). Ideal and minimally acceptable DGIs were determined for each size group. To evaluate the effect of target shape on DGI criteria, the plans were divided into 4 target shape groups: (1) homogeneous shape (circular), (2) adjacent to radiosensitive organs at risk (adjacent), (3) irregularly shaped (irregular), and (4) multiple target plans (multilesion). The mean for each target size group was defined as the ideal DGI. Minimally acceptable DGI criteria are specified to reject the lowest 10% of cases. RESULTS: The minimal acceptable DGIs were 83 (Group I), 72 (II), 65 (III), 58 (IV), 52 (V), and 35 (VI). The ideal DGI is designated to evaluate SRS/SRT plans for homogeneous circular lesions, whereas minimal DGI is chosen to assess the plans for irregular, adjacent to organs at risk, and multilesions. SRS/SRT plans with higher DGI values are correlated with lower irradiated normal tissue volumes. CONCLUSIONS: This study provides a table of DGIs for brain SRS/SRT treatments as a tool for assessing the quality of intracranial SRS/SRT plans. DGI guidelines support SRS/SRT planning that results in lower risk of radionecrosis.

De novo cavernous malformation arising in the wall of vestibular schwannoma following stereotactic radiosurgery: case report and review of the literature.

We report a novel case of a radiation-induced cavernous malformation developing in a vestibular schwannoma previously treated with stereotactic radiosurgery. Eleven years after treatment, the patient presented with a large predominantly cystic lesion in the cerebellopontine angle. We performed surgery, and a solid vascular lesion was identified within the schwannoma, which was determined to be a cavernous malformation after histopathological analysis. We review the literature of radiation-induced cavernous lesions, illustrating that while rare, these lesions do pose concern as a long-term complication of brain radiation therapy. We also discuss the possibility that radiation-induced cavernous malformation-like lesions are pathologically distinct from cavernous malformations.

Twenty-five year outcome of sequential abdominal radiotherapy and melphalan:implications for future management of epithelial carcinoma of the ovary.

OBJECTIVE: The purpose of the present study is evaluation of the long-term efficacy of sequential abdominopelvic radiotherapy and melphalan in the management of ovarian carcinoma. METHODS: From 1970 to 1976, 94 women with stages I-III epithelial ovarian carcinoma enrolled in a prospective nonrandomized clinical trial were prescribed 20 Gy to the upper abdomen and 50 Gy to the pelvis followed by courses of melphalan (1 mg/kg/course). Primary endpoints were survival, recurrence, and toxicity. RESULTS: There were 19 stage I, 25 stage II, and 50 stage III patients. For all stages, overall survival was 42% at 5 years, 30% at 10 years, and 17% at 25 years. Median follow-up of the survivors was 24 years. Disease-free survival was 48% at 5 years and remained at 45% from 10 to 25 years. All but two recurrences occurred within the first 27 months. No recurrence or treatment-related death occurred after 8 years. No recurrence was salvaged. All but one initial recurrence was within the peritoneal cavity. Of the 31 patients undergoing a second-look surgical procedure, 84% were free of tumor. Only 8% of patients recurred after a negative second look. Stage and the presence of palpable postoperative disease were significant prognostic factors. Disease-free survivals were 95% from 5 to 25 years for stage I, 70% at 5 years and 60% at 25 years for stage II, and 20% from 5 to 25 years for stage III (P < 0.0001). Although no patient with postoperative palpable tumor was cured, 25% lived beyond 2 years. Stage III patients without postoperative palpable tumor achieved a 47% 25-year disease-free survival. Acute toxicity was acceptable, and 98% of patients completed radiation therapy. Chronic toxicity included a 12% small bowel obstruction rate and a 3% fatal second malignancy/hematological toxicity rate (two cases of acute myelocytic leukemia, one case of thrombocytopenia). CONCLUSIONS: The long-term disease-free survival obtained with abdominopelvic radiotherapy followed by single alkylating agent chemotherapy has not been exceeded by three subsequent decades of multiagent chemotherapy trials. Abdominal radiotherapy may be useful to consolidate complete responses following therapy multiagent chemotherapy, particularly with the upper abdominal dose escalation provided by intensity modulated radiation therapy and possibly in conjunction with chemotherapy.