Acute Radiation Side Effects of Proton Versus Photon Therapy Following Surgery for Early Breast Cancer, a Substudy of the Randomized Controlled Danish Breast Cancer Group Proton Trial.
Kristine Wiborg Høgsbjerg, Stine Elleberg Petersen, Else Maae et al.
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In 30 seconds
This preplanned substudy of a phase 3 randomized trial compared acute side effects of moderately hypofractionated proton therapy (PT) and photon radiation therapy (γRT) after surgery for invasive breast cancer or ductal carcinoma in situ. It included 167 patients with 186 treated breasts, selected for expected high cardiac and/or pulmonary dose with γRT. Grade 2 to 3 dermatitis peaked at week 5 and was more frequent with PT than γRT (71% PT vs 20% γRT); other grade 2 to 3 skin effects were also more common with PT. These skin effects resolved within 2 to 4 weeks, while non-skin effects were similar between groups.
Key findings
- Grade 2 to 3 dermatitis occurred in 71% PT vs 20% γRT, peaking at week 5.
- Pruritus (20% vs 5%) and local pain (17% vs 4%) were also more frequent after PT than γRT.
- All grade 2 to 3 skin effects resolved to grade 0 to 1 within 2 to 4 weeks after peaking.
- Respiratory symptoms, dysphagia, fatigue, and arm/shoulder effects were mild or comparable; no treatment discontinuations occurred.
Why it matters
The randomized comparison provides prospective evidence about acute tolerability of proton versus photon treatment in patients expected to receive high cardiac and/or pulmonary doses with photon planning. The main trade-off was more frequent, but transient, skin toxicity with PT; other reported acute effects were similar. This helps characterize the short-term side-effect profile of modern, moderately hypofractionated treatment.
What to keep in mind
Follow-up for acute side effects extended only to 6 months, so these findings do not establish comparative long-term toxicity.