(P-334) Socioeconomic Status and Prognosis in Premenopausal Breast Cancer: A Population-based Cohort Study in Denmark

Background: Data on how socioeconomic status (SES) influences the effectiveness of cancer-directed treatment in premenopausal breast cancer patients is scarce.

Objectives: To estimate the association between individual-level SES and breast cancer recurrence and mortality, in a cohort of Danish premenopausal breast cancer patients treated with taxane-based chemotherapy.

Methods: From the Danish Breast Cancer Group (DBCG) clinical database, we assembled a cohort of all premenopausal women aged 18–55 years who were diagnosed with non-metastatic breast cancer and prescribed docetaxel-based chemotherapy during 2007–2011. The DBCG database provided comprehensive details on tumor and treatment characteristics. Danish population-based registries provided data on comorbidities, death, and SES at diagnosis. SES included marital status: married (including living with a partner) and single (never married/divorced/widowed); education level: low (~9-11 years of schooling), intermediate (~12-13 years) and high (~14-20 years); income (low, medium or high based on sample tertiles), and employment (employed, unemployed or health-related work absenteeism). Follow-up began 6 months after diagnosis (to approximate the end of chemotherapy) and continued to 10 years, recurrence, death, or 31 December 2016, whichever occurred first. We computed incidence rates (IRs) per 1,000 person-years (PYs) and cumulative incidence proportions of recurrence and death. We used Poisson regression to calculate incidence rate ratios (IRRs) and 95% confidence intervals of recurrence and death according to SES, adjusting for patient, tumor, and treatment characteristics.

Results: Our cohort included 2,616 women. At diagnosis, 35% of the study cohort were single, 17% had low education, 4% were unemployed and 11% had health-related work absenteeism. During follow-up, 286 developed recurrent breast cancer (median follow-up: 6.7 years) and 223 died (median follow-up: 7.2 years). Compared with married women, we observed increased risk of recurrence and death in single women, mainly those with ER+ tumors prescribed tamoxifen. Women with ER+ tumors and health-related work absenteeism had increased mortality compared with their employed counterparts. After adjustment, increased risk of recurrence or mortality attenuated in women with low income or education.

Conclusions: We found unfavorable prognosis among single women and women with health-related work absenteeism; this may be partly related to tamoxifen adherence.