Definitive chemoradiation followed by stereotactic body radiotherapy boost for inoperable endometrial cancer

Objectives For inoperable endometrial cancer (ECA) patients, definitive chemoradiation with stereotactic body radiotherapy (SBRT) boost may be an option. SBRT schedules and dose distributions approximate brachytherapy boost (BB) radiobiologic dosing, while eliminating the need for applicator placement and thus anesthesia. We report toxicity, disease control, and quality-of-life outcomes of a multi-institutional series of SBRT for ECA. Methods Twenty-three patients met the following eligibility criteria: (1) primary ECA, (2) contraindication or refusal of BB, and (3) need for definitive radiation (RT). Prior to SBRT, patients received pelvic RT +/- nodal boost concurrent with cisplatin. SBRT dose of 25.0-35.0 Gy was prescribed to a high-risk clinical target volume (HR-CTV) in 4-5 fractions. Assessments included (1) post-treatment disease surveillance, (2) toxicity using the U.S. National Cancer Institute's CTCAE scales, and (3) quality-of-life using FACT-G. Results Median follow-up was 31 months. BB was infeasible due to medical comorbidities, patient refusal, and technical contraindications (73.9%, 21.7%, and 4.3%, respectively). Most patients were FIGO stage I (60.8%). Mean cumulative dose to high-risk clinical target volume (HR-CTV) was 88.94 Gy (range 75.50-93.83 Gy). Mean SBRT dose to 95% of the planning target volume (PTV) was 32.55 Gy (range 25.00-35.77 Gy), and mean PTV receiving 100% of the dose was 95.29% (range 91.48-99.01%). No patients had grade 2+ long-term gastrointestinal or genitourinary toxicity. Locoregional and distant control was 91.6% at 1 year and 85.4% at 2 year. Only one patient died due to ECA at 6 months. Overall survival was 95.0% at 1 year, 74.0% at 2 year, and 59.2% at 5 year. Patient-reported physical and emotional well-being worsened but improved after the acute phase of treatment. Functional and social/family well-being worsened after 1 month. Conclusion Definitive chemoradiation with SBRT boost is safe and effective alternative when BB is not possible.