Tailoring radiotherapy in cT1-2N1 breast cancer to nodal response on primary chemotherapy: 10-year follow-up of RAPCHEM

There is no consensus on indications for postoperative locoregional radiotherapy in cT1-2N1 breast cancer after primary systemic therapy. The previously published 5-year outcomes of the Dutch multicenter prospective RAPCHEM study showed excellent locoregional control when radiotherapy was tailored to the nodal response after primary chemotherapy. Ten-year results of the study have now been published. The study included 833 patients referred to one of 17 centers between 2011 and 2014, with cTi-2N1 breast cancer with ≤ 3 suspicious nodes at imaging treated with primary chemotherapy, followed by breast and axillary surgery. Three risk groups were defined: the low-risk group (n=291) received whole breast radiotherapy after lumpectomy and no radiotherapy after mastectomy; the intermediate-risk group (n=370) received whole breast or chest wall radiotherapy without regional nodal radiotherapy; and the high-risk group (n=177) received whole breast or chest wall radiotherapy and regional nodal radiotherapy of levels III-IV. The 10-year locoregional recurrence rate in all patients was 2.9% (95% CI 1.9-4.2), with 2.4% (1.1-4.7) in the low-risk group, 3.2% (1.8-5.4) in the intermediate-risk group, and 2.8% (1.1-6.1) in the high-risk group. No significant differences were observed in locoregional recurrence rates between the groups. The 10-year recurrence-free interval rate for all patients was 79.2% (76.2-81.1), and the 10-year overall survival rate for all patients was 83.0% (80.3-85.4). The authors conclude that tailoring locoregional radiotherapy in cT1-2N1 breast cancer to the nodal response after primary systemic therapy resulted in a low 10-year locoregional recurrence rate, with promising recurrence-free interval and overall survival.