The applicability of the 21-gene assay to inform chemotherapy benefit in lymph node positive hormone receptor positive male breast cancer.

PURPOSE: Our study aimed to determine if chemotherapy administration based on the 21-gene Oncotype DX Recurrence Score (RS) in men with hormone receptor positive (HR+) Her2 negative (Her2-) lymph node positive(LN+) breast cancers (BC) impacted overall survival (OS).

PATIENTS AND METHODS: We conducted a retrospective cohort study on adult men and women with HR+ Her2-, 1-3 axillary LN + BC, with a valid oncotype DX RS assay, diagnosed between the years 2004-2020, using the National Cancer Database. RS risk categories were defined as low risk: 0-13, intermediate risk:14-25, and high risk: ≥26.

RESULTS: Of the 77,820 patients included in the study, 900 (1.2%) were male and 76,920 (98.8%) were female. Higher RS (both as a continuous and categorical variable) was significantly associated with worse OS in males (p = 0.003 continuous, p = 0.006 categorical), females ≤ 50 years old and females > 50 years old (p < 0.001 both continuous and categorical, in both groups). In the stratified adjusted models, there was no association between receipt of chemotherapy and OS in males for all RS risk groups. Conversely, chemotherapy improved OS for women ≤ 50 and for women > 50 who belonged to the intermediate and high RS risk groups (p = 0.001 and p < 0.001 respectively (women ≤ 50); p = 0.005 and p < 0·001 respectively (women > 50)).

CONCLUSION: RS as determined by the Oncotype DX assay is associated with OS in men and women with HR+ Her2- LN+ BC. However, RS is not an indicator of the benefit of chemotherapy on OS in men, in contrast to women, with HR+ Her2- LN+ BC.