21-Gene recurrence score influences the chemotherapy decision for patients with breast cancer of different luminal subtypes.

Luminal subtypes and the 21-gene recurrence score (RS) are important factors in the decision-making process for adjuvant chemotherapy in patients with hormonal receptor (HR)-positive/human epidermal growth factor receptor 2 (HER2)-negative breast cancer. However, their effect on adjuvant chemotherapy decisions in the real world has not been thoroughly investigated, particularly for patients of the luminal A-like subtype with a high RS or the luminal B-like subtype with a low RS. The present study, a total of 772 HR+/HER2- patients who underwent 21-gene testing, were included in a retrospective analysis. The impact of clinicopathological factors and the 21-gene RS on chemotherapy recommendation was analyzed in the whole population and for patients of different luminal subgroups. The results revealed that chemotherapy was highly recommended for patients of younger age, with larger tumor size, node involvement, higher grade, luminal B-like subtype and higher RS. A high RS was identified to be the most important impact factor for chemotherapy recommendation among all patients [odds ratio (OR), 62.54; 95% CI, 25.58-152.92], the luminal A-like group (OR, 435.05; 95% CI, 29.90-6331.06) and the luminal B-like group (OR, 57.20; 95% CI, 22.42-145.96). For patients of the luminal A-like subtype with a high RS or patients of the luminal B-like subtype with low RS, the 21-gene RS was demonstrated to be the most important independent factor for chemotherapy recommendation, with an adjusted OR of 134.52 (95% CI, 10.39-1741.89). In conclusion, luminal subtypes and the 21-gene RS were found to be associated with chemotherapy recommendation for HR+/HER2- patients. For patients with a discordant luminal subtype and 21-gene RS risk, the 21-gene RS score was found to be the most important factor that influences chemotherapy decision, which warrants further clinical evaluation.