21-gene recurrence score testing in the older population with estrogen receptor-positive breast cancer

The 21-gene recurrence score (RS) (Oncotype Dx, Genomic Health, Redwood City Ca) has not been validated in an older cohort with estrogen receptor (ER)-positive breast cancer. The objective of this study was to evaluate RS validity in a group of older women with ER-positive breast cancer.

Utilizing the Surveillance, Epidemiology, and End Results Program (SEER) database with available RS, we evaluated women with ER-positive breast cancer aged 18-69 and those 70 years of age and older from 2004 to 2014. We utilized multivariable logistic regression models to evaluate factors associated with RS testing as well as a high-risk categorization for those who underwent testing. Survival was analyzed using Kaplan Meier curves and Cox proportional hazard models.

We identified 363,876 women aged 18-69 years and 147,107 women aged 70 years and older. A smaller proportion of patients in the older group (8%) underwent RS testing than in the younger group (18%). Of the patients who underwent testing, distribution of RS was similar between groups. High-risk categorization independently predicted a higher likelihood of death for older patients (hazard ratio 1.47, 95% confidence interval 1.15-1.90). Among patients with high-risk RS, chemotherapy was associated with a decreased risk of death in the younger group, but not in the older group.

Older women are less likely to receive RS testing, but when tested, older patients have a similar distribution of RS as compared to younger patients. While high-risk categorization in the older cohort was prognostic, chemotherapy was not associated with improved survival.