Preoperative radiotherapy (preop-RT) can be used as one strategy to improve pathological complete response rates in locally advanced breast cancer. Hence, we conducted a pilot study of preop-RT in partial responders to primary systemic chemotherapy (PST).

Standard PST comprising of four cycles of Adriamycin/cyclophosphamide followed by four cycles of taxanes (along with trastuzumab in Her2-neu enriched) was initiated. After two cycles of taxanes, partial responders (PRs) were enrolled onto preop-RT (40 Gy/15#/3 weeks to whole breast followed by boost dose of 10 Gy/4#/1 week to gross tumor with 5 mm margin [clinical target volume] and 10 mm margin [planning target volume] by three-dimensional conformal radiation therapy. Field-in-field technique was used whenever the need to correct dose heterogeneity arose. The remaining two cycles of taxanes were completed 3 weeks after the completion of RT. Surgical intervention was initiated 6 weeks after the completion of PST. The intention of such a strategy was to keep an interval of 12 weeks between completion of RT and surgery to achieve maximum downstaging. The primary endpoint was pathological complete response rate (ypCR).

Twenty-one women were enrolled (median age 47 years, 35% premenopausal, 50% upper outer quadrant, 65% T4, 85% node positive, 40% luminal A, 10% luminal B, 15% Her-2-neu enriched, and 35% triple-negative breast cancer [TNBC]). Twenty-eight percent underwent breast conservation and the rest modified radical mastectomy (n = 13) and 2 did not undergo surgery (elderly [n = 1], lost to follow-up [n = 1]). ypCR(T) rate was 53% and ypCR(N) was 59%. ypCR(T) rate was 50% in Her-2 positive and 25% in TNBC, and 33.3% in luminal A. At a median follow-up of 24 months, the median overall survival is 41 months and 2 (both TNBC, ypCR, and ypPR) developed distant metastasis (in lung and soft tissue).

This pilot study reveals encouraging results in high-risk subsets and this potential of preop-RT should be explored further in larger studies.

This work has been approved by the institute's Ethics Committee.

S.A. was involved in the study design, data collection and analysis, as well as manuscript writing. A.G. contributed to data analysis. G.C. facilitated patient recruitment, performed the surgeries, and analyzed postoperative complications.

This work has been presented in UP AROI, Breilly, 2022, and won the best paper award.

Received: 24 May 2023

Accepted: 18 April 2025

Article published online:
15 May 2025

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