Treating the Thyroid as an Organ at Risk in Supraclavicular Breast Irradiation

In an interview at the 2026 American Society for Radiation Oncology (ASTRO) Annual Meeting, Nikolai Strusberg, MD, a radiation oncology research fellow in the Department of Radiation Oncology at Herbert Wertheim Cancer Institute, Baptist Health South Florida, discussed the broader implications of a retrospective study comparing intensity-modulated proton therapy (IMPT) with photon-based intensity-modulated radiation therapy (IMRT) for supraclavicular irradiation in breast cancer.

Strusberg noted that the study did not assess other toxicities, though research is ongoing on heart, lung, and skin doses and on capsular contracture. He referenced prior work from his group linking proton therapy to a higher risk of capsular contracture in the post-mastectomy reconstruction setting. Rather than changing practice, he said, the study highlighted that the thyroid should be considered an organ at risk in every supraclavicular treatment plan. He also described an upcoming analysis of the group’s proton cohort that will evaluate linear energy transfer as a possible source of capsular contracture.

Transcript:

Were there other toxicity differences between the 2 approaches worth noting?

Strusberg: We didn’t study any other toxicities in our retrospective cohort. It is important to say that there are large series and studies right now looking at heart doses, lung doses, skin doses, and capsular contracture, for instance, which are very troublesome and worrisome [adverse] effects. Last year, our group had an oral presentation and published a manuscript showing how, interestingly, protons were associated with a higher risk of capsular contracture in patients who were also treated to the supraclavicular fossa.² At this point, we don’t know.

I don’t think this is a study that should change practice. What I think this study emphasizes, and what it made possible for us as physicians to notice, is that the thyroid should be considered an organ at risk in every single plan. The message here is that for every patient with breast cancer who needs treatment to the supraclavicular fossa, we need to aim for an adequate target field while also keeping in mind the thresholds for the organs at risk, especially the thyroid, because we know it’s a bothersome side effect that can eventually develop down the road.

What are the next steps for this research?

Strusberg: We are currently finalizing a study on the capsular contracture patients we discussed from last year, which we aim to publish this year or next year. Right now, we’re looking only at our proton cohort and evaluating something called linear energy transfer, because we want to determine the source of this very painful side effect in patients treated with protons.

Refernces

1. Zerey MM, Gal O, Feenstra NA, et al. Does pencil beam scanning proton therapy impart a higher risk of capsular contracture when compared with intensity modulated photon radiotherapy in the post-mastectomy reconstruction setting? Int J Radiat Oncol Biol Phys. Published online April 18, 2026. doi:10.1016/j.ijrobp.2026.04.011

2. Strusberg N, Herrera R, Wang D, et al. Does intensity modulated proton therapy reduce clinical hypothyroidism after supraclavicular irradiation for breast cancer? Presented at: 2026 ASTRO Annual Meeting; September 26–30, 2026; Boston, MA. Poster 2831.