Background: Women who live in rural and urban settings have different outcomes for breast cancer. A 21-gene assay predicts 10-year distant recurrence risk and potential benefit of chemotherapy for women with hormone receptor-positive (HR+) breast cancer.
Objective: To assess differences in scores and cancer therapies received by rural versus urban residence.
Methods: We conducted a multi-institutional retrospective chart review of breast cancer patients diagnosed 2005-2010 with score results. Comparisons by rural versus urban residence (determined by rural-urban commuting area (RUCA) codes derived from zip codes) were made using the Fisher exact test for discrete data such as recurrence score results (<18 vs >18; score range, 0-100, with lower results correlated with less risk of distant recurrence), stage, and receptor status. The Wilcoxon rank sum test was used for continuous data (score results 0-100 and age.) All tests were at a 2-sided significance level of .05.
Results: 504 patients had RUCA codes (92% white, 62% postmenopausal). For rural (n = 135) compared with urban (n = 369) patients, the median scores were 16 and 18, respectively, P = .18. Most of the patients received endocrine therapy, 123 of 135 (91%) rural, compared with 339 of 369 (92%) urban (P = .19). For scores 18-30, 20 of 56 (36%) rural patients, compared with 82 of 159 (52%) urban patients received chemotherapy (P = .03).
Limitations: Limitations include lack of randomization to receipt of the assay.
Conclusions: Recurrence score results did not significantly differ between women based on residence, although women living in a rural area received significantly less chemotherapy for scores >18. This suggests that for HR-positive breast cancer, discrepancies between rural and urban residence are driven by treatment factors rather than differences in biology.
Funding: Genomic Health Inc
Keywords: OncotypeDX; breast cancer; gene assay; recurrence score; rural-urban disparities.