Breast re-irradiation achieved 84.2% five-year recurrence-free survival with 3.9% grade 3 toxicity

KEY POINTS

• This retrospective single-institution cohort included 113 consecutive patients receiving curative-intent external-beam breast or chest-wall re-irradiation after surgical resection of an ipsilateral recurrence between 2010 and 2024. Median follow-up was 67.1 months.
• Median interval between radiation courses was 12.3 years, median re-irradiation dose was 45 Gy, and median cumulative EQD2 was 94.9 Gy. Treatment used 3D conformal radiotherapy in 74.3% and IMRT in 25.7%.
• Long-term disease control was favorable. Five-year locoregional recurrence-free survival was 84.2% (95% CI 76.7-92.4), overall survival was 82.1%, and cumulative local failure was only 6.8%.
• Severe late toxicity remained uncommon despite repeat irradiation. Five-year cumulative grade ≥2 toxicity was 35.4%, but grade 3 toxicity was only 3.9%, with no grade 4 or 5 events.
• Cumulative radiation dose was the strongest independent toxicity predictor. Each additional 10 Gy EQD2 nearly doubled grade ≥2 toxicity risk (sHR 1.94, p<0.001) and was associated with a more than fourfold increase in grade 3 toxicity risk (sHR 4.32, p<0.001).
• Technique mattered substantially. Five-year grade ≥2 toxicity was 15.0% with IMRT versus 43.4% with 3DCRT, and IMRT remained independently protective on multivariable analysis (sHR 0.40, p=0.005). A longer interval between radiation courses was also associated with lower toxicity.
• Among early-stage recurrences, partial breast or chest-wall re-irradiation did not compromise locoregional control compared with whole-volume re-irradiation. Conversely, locally advanced disease and second or subsequent recurrence were independently associated with worse recurrence-free survival.

CLINICAL TAKEAWAY

SOURCE

Cancers