The positive non-sentinel status is not the main decisional factor for chemotherapy assignment in breast cancer with micrometastatic disease in the sentinel lymph node

Background Surgical and systemic treatment modalities for breast cancer (BC) patients with micrometastatic disease in the sentinel lymph node biopsy (SNB) are controversial. The aim of this study was to evaluate decisional factors associated with assignment of adjuvant chemotherapy (CT). Patients and Methods In a retrospective multicentric European study we evaluated cases of primary BC patients who underwent SNB. Logistic regression (LR) and recursive partitioning analyses (RPA) were performed to determine factors associated with CT. Results Of the 172 patients with micrometastatic disease, 39.5% received adjuvant CT. In the group treated with CT, patients tended to be younger (P = 0.001), with higher grade (P = 0.001) and HER2 positive tumors (P = 0.006) compared to patients without CT. In multivariate LR, age (P = 0.0027), high grading (P = 0.01) HER2 positivity (P = 0.03), and positive non-SN status (P = 0.03) were significantly associated with CT. RPA demonstrated that tumor grade, and not the non-SN status, was the first split in the partition tree followed by HER2 status, and non-SN status influencing the probability for CT administration. Conclusion High tumor grade is the main decisional factor followed by HER2 positivity and then by the positive non-SN status for CT in micrometastatic disease in the SN.