Factors Associated with the Use of Gene Expression Profiles in Estrogen Receptor-Positive Early-Stage Breast Cancer Patients: A Nationwide Study.

BACKGROUND: Breast cancer guidelines suggest the use of gene expression profiles (GEPs) in estrogen receptor-positive (ER+) breast cancer patients in whom controversy exists regarding adjuvant chemotherapy benefit based on traditional prognostic factors alone. We evaluated the current use of GEPs in these patients in the Netherlands.

PATIENTS AND METHODS: Primary breast cancer patients treated between January 1, 2011 and December 31, 2014 and eligible for GEP use according to the Dutch national breast cancer guideline were identified in the Netherlands Cancer Registry: ER+ patients <70 years with grade 1 tumors >2 cm or grade 2 tumors 1-2 cm without overt lymph node metastases (pN0-Nmi). Mixed-effect logistic regression analysis was performed to associate characteristics of patients, tumors and hospitals with GEP use.

RESULTS: GEPs were increasingly deployed: 12% of eligible patients received a GEP in 2011 versus 46% in 2014. Lobular versus ductal morphology (OR 0.58, 95% CI 0.47-0.72), pN1mi status (versus pN0, OR 0.52, 95% CI 0.40-0.68), and tumor size (>3 cm vs. >2 cm, OR 0.33, 95% CI 0.14-0.88) were inversely associated with GEP use. High socioeconomic status (SES) (OR 1.32, 95% CI 1.06-1.64) and younger age (OR 0.96/year increasing age, 95% CI 0.95-0.96) were positively associated with GEP use. GEP use per hospital did vary, but no predefined institutional factors remained independently associated with GEP use.

CONCLUSION: GEP use increased over time and was influenced by patient- and tumor-associated factors as well as by SES.