Prioritizing Proton Therapy for Pelvic Nodal Irradiation in Prostate Cancer

In an interview with CancerNetwork®, at the 2026 American Society for Radiation Oncology (ASTRO) Annual Meeting, Marcio A. Fagundes, MD, discussed the clinical scenarios that most strongly support prioritizing proton therapy over photon-based modalities in patients with intermediate- to very high–risk prostate cancer.

In Fagundes’ institutional study of 404 patients treated with intensity-modulated proton therapy between 2018 and December 2023, most patients with high- and very high–risk disease received pelvic nodal irradiation. He noted that his group is planning a multi-institutional study to define which end points best capture the difference between proton therapy and conventional radiation when pelvic lymph nodes are treated. Candidate end points include chronic diarrhea, bowel urgency, and other changes in quality of life.

Fagundes is vice chair of Radiation Oncology, director of International Outreach, and a radiation oncologist at Baptist Health Herbert Wertheim Cancer Institute (WCI) in Miami, Florida.

Transcript:

CancerNetwork: For multidisciplinary tumor boards weighing intensity-modulated proton therapy against advanced photon-based modalities such as ultrahypofractionated stereotactic body radiotherapy (SBRT) or volumetric modulated arc therapy, what scenarios in intermediate- to very high–risk disease provide the strongest justification for prioritizing proton therapy?

Fagundes: Prioritizing proton therapy is most justified, or easiest to demonstrate, when we are treating the pelvic lymph nodes. Current practice guidelines determine that we have to include the lymph nodes up to the iliac bifurcation, which is usually at the L4 [or] L5 level. That includes a significant extent of the pelvis; virtually the entire pelvic nodal chain is included. Proton therapy will decrease [dosage] to the bowel and minimize adverse effects. That is the justification for using it.

SBRT, or stereotactic body radiotherapy, involves only 5 sessions, given every other day, for example. It is primarily recommended for low- and intermediate-risk prostate cancer, not for patients in whom we are treating the pelvic nodes. When you are treating pelvic nodes, doing 5 fractions is still a developing paradigm. We are primarily treating [patients with] low- and intermediate-risk disease in 5 sessions, not those who need pelvic lymph node treatment.

Reference

Fagundes MA, Hassan H, Rodrigues M-A, et al. Intensity modulated proton therapy (IMPT) for localized prostate cancer: disease control outcomes in intermediate to very-high risk patients. Presented at: 2026 ASTRO Annual Meeting; September 26-30, 2026; Boston, MA. Abstract PQA 06.