Top Line: Available data suggest proton breast radiation can result in worse skin effects than expected.
The Study: A single-institution prospective registry study compared skin adverse effects among 176 women receiving conventionally fractionated post-mastectomy radiation (50 Gy in 25 fractions) with either IMPT (n=93) or photons (n=83, predominantly 3DCRT). Investigators prospectively compared physician-assessed dermatitis, patient-reported skin outcomes, and detailed skin dosimetry. Importantly, plans explicitly contoured skin (i.e., 3-mm inner margin from body contour) with dose objectives of D90% ≥90% of prescription to cover dermal lymphatics. Proton plans additionally constrained skin D1cc ≤105% (ideally ≤96%) to limit adverse effects. The chest wall target was cropped from skin, and photon plans used a 5-mm planning target volume also cropped from skin as well as lung while proton plans used robust optimization in lieu of a planning target volume. Despite historical concerns regarding proton-associated dermatitis, rates of acute grade 2+ dermatitis were nearly identical (47% proton vs 48% photon), with low rates of grade 3 dermatitis (3% vs 7%). Patient-reported outcomes were also largely comparable, although patients receiving photons reported more persistent skin color changes at 12 months (26% vs 6%). What mattered most across modalities were higher skin hotspot metrics (D1cc, D10cc, V105%) that strongly correlated with dermatitis risk.
TBL: Post-mastectomy radiation dermatitis appears less about modality and more about meticulous avoidance of hotspots within skin. | Gergelis, Int J Radiat Oncol Biol Phys 2026
The Study: A single-institution prospective registry study compared skin adverse effects among 176 women receiving conventionally fractionated post-mastectomy radiation (50 Gy in 25 fractions) with either IMPT (n=93) or photons (n=83, predominantly 3DCRT). Investigators prospectively compared physician-assessed dermatitis, patient-reported skin outcomes, and detailed skin dosimetry. Importantly, plans explicitly contoured skin (i.e., 3-mm inner margin from body contour) with dose objectives of D90% ≥90% of prescription to cover dermal lymphatics. Proton plans additionally constrained skin D1cc ≤105% (ideally ≤96%) to limit adverse effects. The chest wall target was cropped from skin, and photon plans used a 5-mm planning target volume also cropped from skin as well as lung while proton plans used robust optimization in lieu of a planning target volume. Despite historical concerns regarding proton-associated dermatitis, rates of acute grade 2+ dermatitis were nearly identical (47% proton vs 48% photon), with low rates of grade 3 dermatitis (3% vs 7%). Patient-reported outcomes were also largely comparable, although patients receiving photons reported more persistent skin color changes at 12 months (26% vs 6%). What mattered most across modalities were higher skin hotspot metrics (D1cc, D10cc, V105%) that strongly correlated with dermatitis risk.
TBL: Post-mastectomy radiation dermatitis appears less about modality and more about meticulous avoidance of hotspots within skin. | Gergelis, Int J Radiat Oncol Biol Phys 2026