3791 - Evaluation of Proton Beam Radiotherapy In Ovarian Cancer: Analysis of the Multicenter Proton Collaborative Group Prospective Registry
Presenter(s)
R. Padmanabhan1,2, I. Yacoub1,3, A. M. Chhabra1,4, I. J. Choi1,3, J. Tang1,5, D. C. Marshall1,4, J. R. Bloom1,4, V. Gupta4, L. L. Lin6, S. E. James7, A. D. Thukral Jr8, E. M. Nichols9, J. Zeng10, C. E. Vargas7, K. M. Alektiar1,3, K. J. Mehta1,5, C. B. Simone II1,11, and K. Hsieh1,4; 1New York Proton Center, New York, NY, 2Department of Radiation Oncology, Brooklyn Methodist hospital, Brooklyn, NY, 3Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY, 4Department of Radiation Oncology, Mount Sinai Health System, New York, NY, 5Department of Radiation Oncology, Montefiore Einstein Cancer Center, Bronx, NY, 6Department of Radiation Oncology, MD Anderson Cancer Center, Houston, TX, 7Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ, 8Department of Radiation Oncology Northwestern Medicine, Warrenville, IL, 9Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, 10Department of Radiation Oncology, University of Washington/Fred Hutchinson Cancer Center, Seattle, WA, 11Memorial Sloan Kettering Cancer Center, New York, NY
Purpose/Objective(s): There is limited published literature regarding the use of proton beam therapy (PBT) in the management of ovarian cancer. We sought to evaluate clinical outcomes and adverse events (AEs) of patients with ovarian cancer enrolled in the Proton Collaborative Group (PCG) prospective, multi-institutional registry and treated with PBT.
Materials/Methods: All consecutive patients with ovarian cancer enrolled in the PCG registry and treated with PBT between February 2013 and September 2025 were included. Patient and disease characteristics, prior treatments, PBT details, and AEs were summarized using descriptive statistics. Continuous variables were reported as median with interquartile range (IQR) and categorical variables as percentages. Locoregional recurrence-free survival (LRFS) and overall survival (OS) were estimated with Kaplan-Meier method.
Results:
The cohort included 38 patients with a median age of 66 years (IQR 58-73). Most patients were White (82%) with ECOG performance status of 0-1 (71%). Approximately two-fifths of patients (39%) had high-grade ovarian histology, defined as serous carcinoma, clear cell carcinoma, carcinosarcoma, and grade 3 or higher disease. At the time of PBT, 71% were treated for recurrent or progressive disease, and 45% had metastatic disease. The majority underwent prior surgical procedures: cytoreductive surgery (32%), hysterectomy with bilateral salpingo-oophorectomy (16%), or both (13%). Additionally, 87% had prior chemotherapy, and 34% had prior radiotherapy. The majority received non-palliative PBT (63%) without concurrent chemotherapy (100%). PBT completion rate was 92% (35/38); three patients discontinued treatment due to disease progression (n=1), AEs (n=1; CTCAE grade (G) 2 diarrhea, esophagitis, dysphagia, and abdominal pain), or both (n=1; G3 fatigue, G2 constipation, pain, and diarrhea). Acute and late =G3 AEs were limited to G3 fatigue (n=1), G3 anorexia (n=1), and G3 hip fracture (n=1) Of the 87% receiving PBT to the abdominopelvic region, the median external beam radiotherapy dose was 54 Gy (IQR 45-60) in 25 fractions (IQR 15-28). For the subset with post-PBT follow-up data (n=25), the median follow-up was 12.4 months (IQR 5.1-22.1) with a locoregional control rate of 96%. LRFS was 80% and 66% at 6 and 12 months, respectively. OS was 84% and 69% at 6 and 12 months, respectively.Conclusion: PBT was generally well-tolerated among patients with ovarian cancer, with few experiencing severe AEs. Additional study focusing on the impact of PBT on disease control and symptom palliation is warranted.