Long-term cosmetic outcome after intraoperative radiotherapy boost with low-energy X-rays in breast-conserving therapy: a pooled cohort analysis of the TARGIT-BQR and ROKSM trials

Abstract Purpose This study investigates objective long-term cosmetic outcomes in patients with breast cancer after intraoperative radiotherapy applied as a boost (IORT boost) from a pooled international cohort. Methods A pooled analysis of two prospective studies with IORT boost (low-energy X‑rays, 20 Gy; inclusion criteria: 3.5 cm maximum tumor size and preoperative indication for a boost according to local criteria) during breast-conserving surgery followed by whole-breast radiotherapy (46–50 Gy). The analysis included photos from a subgroup of the prospective phase IV TARGeted Intraoperative radioTherapy (TARGIT) Boost Quality Registry (BQR) study (NCT01440010) with a follow-up of up to 10 years as well as patients from a Swiss study (ROKSM; Spital Thurgau AG; NCT02114086) with a follow-up of 5 years. The pooled analysis included photos from both trials taken at the same timepoints (6 weeks, 6 months, 1 year, 2 years, and 5 years after completion of whole-breast radiotherapy). Cosmetic results were evaluated with the validated BCCT.core software (BCCT.core 2.0, INESC Porto, Portugal) to assess symmetry, color, and scars. A generalized estimating equation (GEE) regression model was used to compare the two cohorts over time. Results The pooled analysis included 777 cosmetic assessments from 276 patients. Across all follow-ups in the pooled analysis, the majority of cosmetic results were rated as excellent or good (61.9%). Patients from TARGIT-BQR had significantly more excellent or good ratings than patients from ROKSM ( p < 0.0001). The proportion of patients receiving “excellent” and “good” ratings remained higher in TARGIT-BQR than in ROKSM at every timepoint during follow-up. Overall, for up to 10 years, the majority of ratings in the whole cohort were “excellent” or “good.” Conclusion In this international pooled analysis, the cosmetic outcome after IORT boost followed by whole-breast irradiation shows a good esthetic long-term outcome. Further studies should explore factors that influence cosmetic outcomes and consider additional treatment-related parameters.