Patient Outcomes Following Proton Beam Therapy for Cervical Cancer: A Multicenter Proton Collaborative Group Prospective Registry Analysis

Background and Aims: Published data on the use of and outcomes for proton beam therapy (PBT) in patients with cervical cancer are limited.This analysis aimed to evaluate clinical outcomes for this patient population in the Proton Collaborative Group prospective registry.Methods: All consecutive patients with cervical cancer who underwent PBT between July 2012-September 2025 were analyzed.Descriptive statistics, locoregional recurrence-free survival (LRFS), and overall survival (OS) measured from the end of PBT were evaluated.Results: The cohort included 39 patients with a median age of 53 years (IQR 42-65.5 years).The majority were White (79.5%) with ECOG performance status of 0-1 (79.5%).Of those with disease staging (n=26), 19.2%, 26.9%, 34.6%, and 19.2% had Stage I, II, III, and IV disease, respectively.Patients received prior chemotherapy (74.4%), hysterectomy (38.5%), and abdominopelvic radiotherapy (33.3%).The majority (92.3%) completed the prescribed PBT course; three patients did not due to patient refusal, declining performance status, or death.Grade ≥3 CTCAE acute and late toxicities were experienced by three patients (G3 fatigue, anemia, and urinary tract pain; two resolved within two weeks) and two patients (G3 chronic kidney disease and G4 respiratory failure), respectively.The patients who underwent curative-intent, abdominopelvic-directed PBT (n=28) received a median external beam radiotherapy dose of 45.1Gy (IQR 45.0-51.6) in 25 fractions (IQR 25-28).Seven patients (25.0%) received a median PBT boost of 9.6Gy (average 13.5, IQR 5.6-19.8) in 8 fractions (average 8.6, IQR 6-12) and 12 (42.9%)received a brachytherapy boost of 25.5Gy (IQR 17.5-29.0)in 5 fractions (IQR 4-5).Three (10.7%) patients received a combined PBT and photon course.Seventeen (60.7%) patients received concurrent chemotherapy with some having Stage ≥III disease (n=6), positive margin (n=1), or both (n=2).For the subset with post-PBT follow-up data (n=22), the median follow-up was 10.8 months.LRFS was 90.4% and 79.8% at 6 and 12 months, respectively.OS was 95.5% and 79.5% at 6 and 12 months, respectively.Conclusions: This is the largest reported cohort of patients with cervical cancer receiving PBT.PBT was well-tolerated with minimal risk of toxicity and offered reasonable early locoregional control.Further study could help tailor PBT indications in this patient population.