Post-chemotherapy target volumes are safe as boost volume for intact breast radiotherapy in locally advanced breast cancer

Abstract

Purpose

The purpose of our study is to evaluate the challenges in identification of postoperative complexes (POC), the utility of clips in delineation of clinical target volume for boost in LABC downstaged with neoadjuvant chemotherapy (NACT) and to correlate this with patterns of recurrence.

Methods and materials

LABC patients who underwent NACT followed by BCS and radiotherapy (2007–2014) were the subject of our analysis. The data on visibility and characteristics of postoperative cavity (POC), concordance of its volume with clip volume on radiation planning scan were retrieved. A 1cm margin beyond POC was delineated as a clinical target volume (CTV). Postoperative whole breast and supraclavicular radiotherapy (50Gy/25fractions/5wk or 42.4Gy/16#/3 wk) followed by boost (10−16Gy/5-8#/1–1.5wk) were delivered. Patterns of recurrence were evaluated.

Results

Out of 60 patients, 28.3% patients had stage II disease and 71.7% had stage III disease. 25% patients achieved pathological CR (complete response). The median POC volume was 30 cc and the median clip volume was 40 cc. The concordance of POC volume with clip volume was seen in 80%. Clips served as a good surrogate for POC in 80% of patients. At a median follow-up of 65 months (IQ range 32–84 months), and a lost to follow-up rate of 11.6 %, 3.3% (n=2) patients had local recurrence (LR) and 8.3% (n=5) had regional recurrence (LRR) in the supraclavicular region.

Conclusions

Delineation of post NACT excision cavity as POC for boost radiotherapy is safe. Clips serve as a good surrogate for CTV delineation in 75% patients.