Purpose Renal cell carcinoma is refractory to conventional radiation therapy but responds to higher doses per fraction. However, the dosimetric data and clinical factors affecting local control (LC) are largely unknown. We aimed to evaluate the safety and efficacy of stereotactic ablative radiation therapy (SAbR) for extracranial renal cell carcinoma metastases. Methods and Materials We reviewed 175 metastatic lesions from 84 patients treated with SAbR between 2005 and 2015. LC and toxicity after SAbR were assessed with Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 and Common Terminology Criteria for Adverse Events (CTCAE) version 4.0. Predictors of local failure were analyzed with χ2, Kaplan-Meier, and log-rank tests. Results In most cases (74%), SAbR was delivered with total doses of 40 to 60 Gy, 30 to 54 Gy, and 20 to 40 Gy in 5 fractions, 3 fractions, and a single fraction, respectively. The median biologically effective dose (BED) using the universal survival model was 134.5 Gy. The 1-year LC rate after SAbR was 91.2% (95% confidence interval, 84.9%–95.0%; median follow-up, 16.7 months). Local failures were associated with prior radiation therapy (hazard ratio [HR], 10.49; P<.0001), palliative-intent radiation therapy (HR, 4.63; P=.0189), spinal location (HR, 5.36; P=.0041), previous systemic therapy status (0–1 vs >1; HR, 3.52; P=.0217), and BED <115 Gy (HR, 3.45; P=.0254). Dose received by 99% of the target volume was the strongest dosimetric predictor for LC. Upon multivariate analysis, dose received by 99% of the target volume greater than BED of 98.7 Gy and systemic therapy status remained significant (HR, 0.12 and 3.64, with P=.0014 and P=.0472, respectively). Acute and late grade 3 toxicities attributed to SAbR were observed in 3 patients (1.7%) and 5 patients (2.9%), respectively. Conclusions SAbR demonstrated excellent LC of metastatic renal cell carcinoma with a favorable safety profile when an adequate dose and coverage were applied. Multimodality treatment with surgery should be considered for reirradiation or vertebral metastasis. A higher radiation dose may be required in patients who received previous systemic therapies.

ObjectiveLocally advanced endometrioid adenocarcinoma (LA-EAC) accounts for the majority of deaths for this cancer, yet there is no consensus on adjuvant treatment after surgery. Past studies suggest that combined modality treatment (CMT) may improve outcomes over treatment with chemotherapy (CT) or radiation therapy (RT, either external beam radiotherapy [EBRT] or vaginal brachytherapy [VBT]) alone. Using a large US-based population-based registry, we evaluated adjuvant CMT in LA-EAC and the relative benefit of regional EBRT compared to focused VBT.MethodsWe studied patients diagnosed with Stage III LA-EAC between 2004 and 2013 from the National Cancer Data Base (NCDB). We used Cox regression and a log-rank test to assess survival based on treatment with CT alone, EBRT alone, VBT alone, or CMT with EBRT and/or VBT. We used a χ2 test to compare covariates between patients receiving CMT with EBRT or VBT.ResultsPatients who received CMT had better survival than those who received CT or EBRT/VBT alone. Compared to CMT with VBT, patients who received CMT with EBRT were slightly older and had more advanced-stage or positive nodes, and fewer had lymph node surgery. We found no survival difference between CMT with EBRT and CMT with VBT even when categorizing patients as high or low risk according to age, grade, and stage (low-risk p=0.3460; high-risk p=0.2158).ConclusionCMT was associated with superior survival outcomes compared to monotherapy. We observed no survival difference between radiation modalities in CMT, which highlights the effectiveness of a more focused treatment like brachytherapy.

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533 Background: Renal cell carcinoma (RCC) has traditionally been refractory to radiotherapy with conventional fractionation, although recent evidence suggests a response to higher doses per fraction. We evaluated local control of extra-cranial metastases from RCC treated with stereotactic ablative radiotherapy (SABR). Methods: RCC patients with extra-cranial metastases treated with SABR were retrospectively enrolled from a single institution between 2005 and 2015. A total of 188 lesions were identified from 91 patients. Radiation (8-60Gy) was delivered in 1-5 fractions (fx) using stereotactic guidance. Local control (LC) was determined by imaging according to RECIST 1.1. Results: Median age at the time of treatment was 62.4 years. Metastases were detected in bone (39.9%), lung (14.9%), liver (9.6%), lymph nodes (11.7%) and other sites (23.9%). Ninety-seven (51.6%) lesions reached curative intent while 91 (48.4%) only reached palliative intent. The most common radiation regimens were 20Gy/1fx, 30Gy/3fx, and 40Gy/5fx. One-year overall survival was 76.5% with a median follow up of 10.7 months. Patients treated with curative SABR showed a 2-fold median survival as compared to those treated with palliative therapy (3.97 year vs 1.43 year, p<0.05). LC rates at 1 and 2 years were 91.4% and 89.7%, respectively. For the patients that failed, median time to local failure was 6.6 months. LC at 1 year significantly improved when treatment was curative (96.1% vs 84.9%, p<0.05), while it decreased in a re-irradiation setting (94.8% vs 46.7%, p<0.05). The median biological equivalent dose (BED) for the lesions that failed was 103Gy, corresponding to 6Gy x 5fx, and was significantly lowered compared to controlled lesions (BED 134Gy). Although 79% of patients developed new lesions within 1 year following SABR, 34.8% did not switch systemic therapy. Switching systemic therapy was delayed in patients treated with curative as compared to palliative SABR (13.4 vs 2.5 months, p<0.05). Conclusions: SABR improved LC of extra-cranial RCC metastases and delayed change to systemic therapy. SABR may complement systemic therapy to improve outcome in the present patient population.

INTRODUCTION Over the past two decades, the treatment of small-to-medium (&lt; 3cm) sporadic vestibular schwannomas (VS) has experienced a definite shift to stereotactic radiosurgery vis-a-vis microsurgery. We performed a systematic review and meta-analysis of VS patients primarily treated with stereotactic radiosurgery (SRS) or microsurgery (MS), with particular attention to hearing preservation outcomes (HPO), tumor control (TC), and facial nerve dysfunction (FND). Materials and METHODS A systematic review was conducted (Medline database) for the period, 2010 to 2020. Studies with mean/median follow-up of &gt;/= 3 years were included. Studies had to report an acceptable standardized hearing metric. HPO, TC, and treatment complications (with special attention to FND) were compared between the MS and SRS groups. RESULTS Thirty-two studies met our inclusion criteria: 10 for microsurgery and 23 for radiosurgery (one comparative study included in both arms). HPO were comparable between MS group and SRS group (56% and 59%, p=0.1527). TC was significantly better in MS group (98%) versus SRS group (92%) [p &lt; 0.0001]. FND was significantly higher in MS group (11%) versus SRS group (2%) [p &lt; 0.0001]. CONCLUSION The ability to diagnose small sporadic VS earlier, allows patients time to consider all possible treatment options which include observation, radiosurgery, or microsurgery. The data presented in this study will assist physicians in their ability to appropriately counsel patients on the benefits and risks of both treatment modalities with the most recent evidence on the factors that contribute greatly to patients’ quality of life: HPO, TC and FND.