B. Elgohari1, M. Mohammed1, H. Wang2, C. J. Houser1, E. Doraisamy1, H. Kim1, and P. N. Barry1; 1The University of Pittsburgh, Department of Radiation Oncology, Pittsburgh, PA, 2The University of Pittsburgh, Department of Biostatistics, Pittsburgh, PA
Purpose/Objective(s): Stereotactic Body Radiation Therapy (SBRT) is widely accepted as a treatment modality for oligometastatic disease in different cancers including gynecological malignancies. Limited data exists for the use of SBRT in oligometastatic uterine cancer. We aimed to evaluate our institutional outcomes utilizing SBRT in treating oligometastatic disease in uterine cancer. Materials/
Methods: A single institute retrospective study under an approved IRB was conducted. Eligible cases were oligometastatic uterine cancer who were received SBRT at our institute. Relevant demographics, clinical, and treatment data were collected. Oncological outcomes including time to in-field local failure (iTTLF), time to locoregional failure (TTLRF), time to distant progression (TTDP), progression free survival (PFS), overall survival (OS) was calculated from SBRT initiation date. All survival Endpoints were analyzed using Kaplan-Meier method. Median survival and confidence interval were calculated. The 6-month, 1-year and 2-year survival probabilities were calculated using SAS (version 9.4, SAS Institute Inc., Cary, NC). Results: A total of 23 uterine cancer cases with 24 oligometastatic sites were identified who received SBRT to metastatic site between 9/2011 to 11/2022. Median follow-up was 30 months (IQR 14-63). Median age at diagnosis was 65 years (IQR: 58-71), 87% white race, 46% endometrioid adenocarcinoma. Initial treatment prior to SBRT included surgery in 96% and all received external bean radiotherapy (EBRT) ± brachytherapy. A total of 21 recurrences with 54% in-field and 33% marginal recurrences were observed. Median SBRT dose, fractions, BED10 were 42Gy (IQR: 35-45), 5 (IQR: 5-5), 77Gy (IQR: 60-86). Median time for re-irradiation was 30 months (IQR 14-81). Nodal recurrences in 58% either pelvic or abdominal were most common sites for SBRT use. Median iTTLF was not reached (95% CI 31-NR). The 6-month, 1- and 2-years LC was 87%, 83%, and 77%, respectively. The median TTLRF was not reached (95% CI 12-NR). The 6-month, 1- and 2-years LRF was 83%, 69%, and 64%, respectively. The median TTDP was 9 months (95% CI 7-NR) with TTDP at 6-month, 1- and 2-years were 74%, 48%, and 48%, respectively. Median PFS was 9 months (95% CI 6-35) with 6-month, 1-and 2-year PFS were 70%, 48%, and 43%, respectively. Median OS was not reached (95% CI 24-NR). The 6-month, 1-and 2-year OS were 100%, 91%, and 73%, respectively. Acute toxicities were observed in 50% of treated areas with 42% grade 1 with fatigue is most common and 8% grade 2 toxicities. Late toxicities were observed in 2 cases (8%) in the form of grade 2 bowel toxicity. No grade 3 or higher were observed. Conclusion: SBRT provides a durable oncological outcome with acceptable toxicity profile in the management of oligometastatic disease in uterine cancer.
