3411 - Clinical Outcomes and Toxicities of Proton Beam Therapy for Testicular Seminoma: Results from the Proton Collaborative Group Prospective Registry
Presenter(s)
L. Zhu1,2, K. J. Mehta1,2, C. B. Simone II2,3, A. M. Chhabra2, K. Hsieh2, I. J. Choi2,4, M. K. Garg2,5, J. Tang2,6, A. D. Thukral Jr7, H. Tsai8, and I. Yacoub2,4; 1Department of Radiation Oncology, Montefiore Einstein Cancer Center, Bronx, NY, 2New York Proton Center, New York, NY, 3Memorial Sloan Kettering Cancer Center, New York, NY, 4Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY, 51Department of Radiation Oncology, Albert Einstein College of Medicine and Montefiore Medical Center, Bronx, NY, 6Department of Radiation Oncology, Montefiore Medical Center, Albert Einstein College of Medicine, and Montefiore Einstein Comprehensive Cancer Center, Bronx, NY, 7Northwestern Medicine Cancer Center and Proton Center, Warrenville, IL, 8ProCure Proton Therapy Center, Somerset, NJ
Purpose/Objective(s):
Testicular seminoma is a highly radiosensitive malignancy affecting predominantly young patients with excellent long-term survival, making minimization of late toxicity and secondary malignancy risk a critical treatment priority. Although photon-based radiotherapy achieves excellent disease control, concerns remain regarding unnecessary radiation exposure to adjacent normal tissues. Proton beam therapy (PBT) offers substantial dosimetric advantages that may reduce these risks; however, clinical outcome data for seminoma remain scarce, particularly in prospective registry settings. We therefore evaluated survival outcomes and treatment-related toxicities among patients with testicular seminoma treated with PBT within a multi-institutional prospective registry.
Materials/Methods:
We reviewed all consecutive patients with histologically confirmed testicular seminoma treated with PBT between 2010 and 2024 and enrolled on a multi-institutional proton therapy prospective registry. Prescribed dose and fractionation were summarized as the cumulative course dose across all treatment phases. Primary endpoints included overall survival (OS), progression-free survival (PFS), and local control. Treatment-related toxicity was graded according to CTCAE v5.0, and survival outcomes were estimated using the Kaplan–Meier method.Results:
Twenty patients were included, with a median age of 38.5 years (Interquartile Range (IQR), 33.5–49.0). Patients were treated using pencil beam scanning or uniform scanning techniques, and all completed their prescribed course of proton therapy. The median total dose was 33.7 GyRBE (IQR, 29.9–36.2), delivered over a median of 17 fractions (IQR, 15–18). Among 11 patients with evaluable follow-up data (median follow-up 23.9 months, IQR, 13.9–45.2), 2-year OS and PFS were both 100% in non-metastatic patients (n=9); both deaths observed in the cohort occurred in patients with metastatic disease at presentation. Local control was achieved in all treated patients, with distant progression observed in two patients, both of whom presented with metastasis before RT. Treatment-related toxicities were predominantly acute (occurring during or within 90 days of RT completion), with the most common being Grade 1–2 fatigue (30%), nausea (30%), and radiation dermatitis (25%). Late toxicities (>90 days after RT end) were reported in 3 patients (15%). No acute or late Grade =3 adverse events and no secondary malignancies were observed during the available follow-up period.Conclusion:
In this registry-based cohort, proton beam therapy for testicular seminoma was associated with excellent local control and a favorable toxicity profile, without Grade =3 treatment-related adverse events. These findings support the feasibility of PBT in this young patient population and highlight the importance of continued follow-up to further characterize late effects and secondary malignancy risk.