Top Line: Can the intensity of adjuvant radiation for node positive breast cancer be modified based on response to neoadjuvant chemotherapy?

The Study: While we eagerly await initial results of B51, here are results from RAPCHEM; BOOG 2010-03, a prospective registry study from the Netherlands. Between 2011 and 2015, patients with clinical T1-2N1 breast cancer treated with neoadjuvant chemotherapy and surgery across 17 centers were enrolled. Lymph node metastasis had to be confirmed histologically, and patients with 4 or more clinically suspicious nodes were not eligible. The study guidelines assigned patients to one of three risk groups based on their nodal response to chemo. Low risk patients were ypN0, and they received whole breast radiation after lumpectomy but no chest wall or regional nodal irradiation (RNI) regardless of axillary surgery technique. Intermediate risk patients had 1-3 residual positive nodes, and they received breast and chest wall radiation with radiation to the low axilla (levels I and II) only if no ALND was performed. High risk patients had 4 or more residual positive nodes, and they received radiation to all of the above plus medial axilla/supraclavicular fossa. Only 6% received internal mammary radiation, though. Of 838 patients, 35% were low risk, 44% were intermediate risk, and 21% were high risk. Overall, 64% of patients actually received radiation according to the study guidelines. Guideline concordant radiation was most frequent in the high risk group (86%) and least in the intermediate risk group (56%). So what was the source of variation? In the low risk group, 37% of patients received more extensive RT than recommended. In the intermediate risk group, 17% received less than recommended RT while 29% received more than recommended. In the high risk group, 14% received less than recommended RT. At 5 years, locoregional-only recurrence was rare (2.2%) and there was no difference in recurrence among risk groups. Any locoregional recurrence occurred in ~5% when counted along with distant recurrences. When looking only at patients treated per the study guidelines, locoregional recurrence remained low at 2.3% for low risk, 1% for intermediate risk, and 1.4% for high risk.

TBL: Response-adapted adjuvant radiation for lymph node positive (1-3) breast cancer treated with neoadjuvant chemotherapy results in a ~2% risk of locoregional recurrence at 5 years across risk groups with fairly de-escalated volumes across the board. | de Wild, Lancet Oncol 2022


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