A study by UPenn and Sloan Kettering. This study reviewed outcomes of the 27 patients with a history of prior radiation and treated with proton therapy for local-regional recurrence of breast cancer. Proton reirradiation regimens included whole breast/chest wall with regional nodal RT (22/27).

The median dose was 51 GyRBE and the most common fractionation was 1.5 Gy twice daily. With a median follow-up 16.6 months, this study reported acute grade 3 toxicities including dermatitis in 2 patients and breast pain in 2 patients. Grade 2 or higher late toxicities included 6 G2 rib fractures and 1 G2 brachial plexopathy, 1 G3 dermatitis, 1 G3 breast pain, and 1 G4 dermatitis.

Twelve patients had new documented recurrences of which 1 was a second in-field LRR, and there were 7 deaths. This study concluded that proton salvage reirradiation to median 51 Gy in 1.5 Gy twice was safe with acceptable acute and late toxicity, and effective with >95% local-regional control.