Clinicopathological characteristics, adjuvant chemotherapy decision and disease outcome in patients with breast cancer with a 21-gene recurrence score of 26-30

Recurrence score (RS) could be used to predict clinical outcomes and chemotherapy efficacy in patients with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative and lymph node-negative breast cancer. However, the clinical features and management of patients with an RS of 26-30 are not completely understood. In the present study, 783 patients with HR+/HER2-, lymph node-negative early breast cancer and RS ≥18 were included and categorized into RS=18-25 (47.8%), 26-30 (25.5%) or ≥31 (26.7%) groups. Clinicopathological characteristics, adjuvant chemotherapy usage and disease outcomes were compared. Alterations in the adjuvant chemotherapy recommendation after 21-gene RS testing were also analyzed. The results indicated that patients with RS=26-30 had higher progesterone receptor (PR) expression [odds ratio (OR)=2.84; P<0.001] and lower Ki-67 index (OR, 1.88; P=0.032) compared with patients with RS ≥31. Multivariate analysis demonstrated that age ≤50 years (OR, 5.75; P=0.001) and luminal-B subtype (OR, 7.75; P<0.001) were factors that were independently associated with chemotherapy usage in the RS=26-30 group. Among 104 patients who were not recommended chemotherapy before 21-gene RS testing, the treatment decision for 52 patients was changed to recommend chemotherapy once an RS of 26-30 was identified. The patient adherence rate to the treatment recommendation was 95.0% (190/200). After a median follow-up of 21.5 months, 6 patients displayed disease recurrence in the RS=26-30 group, and there was no significant difference between patients receiving chemotherapy and patients not receiving chemotherapy. In conclusion, patients with RS=26-30 had tumors with higher PR expression and lower Ki-67 index compared with those of patients with RS ≥31. Age, luminal subtype and RS testing influenced chemotherapy usage in patients with RS=26-30; however, no significant benefit from adjuvant chemotherapy was observed in a short term of 2 years.