The lungs and heart often get all the attention when optimizing breast radiation plans. But what about the shoulder, which is a more common source of complaint after treatment. This post-hoc analysis of the SENOMAC trial (which randomized cN0 breast cancer patients with 1–2 SLN macrometastases to ALND vs. SLN biopsy only) collected RT plans from 868 Swedish patients and auto-segmented the humeral head + 1 cm as a shoulder joint surrogate. Nearly all received locoregional RT (50 Gy/25 fx or hypofractionated equivalent), and dose was converted to EQD2. In the SLN-only group, patients in the highest D0.5cc quartile (≥49.8 Gy) reported significantly worse arm morbidity at 3 years across all measures including physical function score, overhead tasks. They were also more likely to report difficulty lifting heavy objects (42.7% v 28.9%) compared to those with the lowest quartile D0.5cc (<40.4 Gy). The difference was most pronounced in the BCS subgroup. No association was found in the ALND group, likely masked by surgery-related morbidity overwhelming any RT signal. Unfortunately, despite finding a dose-response signal, no clinically actionable thresholds could be identified as the dose range was very narrow (highest quartile 49.8 Gy v lowest quartile 40.4 Gy) and subgroups were relatively small. So, there's a signal that higher max shoulder dose worsens long-term arm morbidity after SLN biopsy, but if you came here hoping for a good threshold, ALARA is what you’re gonna get. | Alkner, Radiother Oncol 2026
