Postdoc Department of Clinical Epidemiology, Department of Clinical Medicine, Aarhus University and Aarhus University Hospital, Aarhus, Denmark Aarhus N, Denmark
Background: The need for social benefits in breast cancer patients may increase following taxane-based chemotherapy due to side effects, including peripheral neuropathy which is crucial for the ability to work. Single nucleotide polymorphisms (SNPs) related to taxane metabolism, transport, toxicity, and neural repair may affect the severity of such side effects.
Objectives: To investigate the association between selected SNPs and ability to work as measured by receipt of social benefits after breast cancer.
Methods: From the Danish Breast Cancer Group clinical database, we obtained data for a cohort of premenopausal women diagnosed with non-distant metastatic breast cancer in 2007–2011, for whom epirubicin- and docetaxel-based chemotherapy was intended. We collected archived breast tumour tissue, extracted DNA, and used TaqMan assays to genotype 21 SNPs related to taxane metabolism, transport, toxicity, or DNA and neural repair. Using Danish population-based registries, we ascertained social benefit payments from one year before to five years after diagnosis. For each week, we categorised women as self-supporting (no benefit registration or student grant), on health-related benefits (including sick-leave and disability pension), and on labour market-related benefits (including unemployment benefits). For each benefit category, we computed incidence rate ratios (IRRs) and 95% confidence intervals (CIs) for variant carriers (hetero- and homozygotes combined) vs. noncarriers during five time periods (-12–0, 0–6, 7–12, 13–24, and 25–60 months post-diagnosis), using negative binominal regression with a robust variance estimator. Covariates were not included, as SNPs are allocated randomly at conception.
Results: Our cohort included 2447 women. Before diagnosis, ~12% received health-related benefits. This increased to ~85% during 0–6 months, declined over the next 18 months, and then stabilised at ~22%. Labour market-related benefits were uncommon (3–6%). Overall, the investigated SNPs were not associated with social benefit receipt. However, variant carriers of GSTP1 (encoding a metabolising enzyme) rs1138272 (n=369) received health-related benefits slightly more often during 0–24 months than noncarriers (n=2053). IRRs (95% CIs) were 1.04 (1.00, 1.08), 1.07 (1.00, 1.14), and 1.13 (1.00, 1.29) during 0–6, 7–12, and 13–24 months, respectively. Conversely, lower use of labour market-related benefits was seen in variant carriers of this SNP, but confidence intervals were wide.
Conclusions: We found little impact of SNPs related to taxane metabolism, transport, toxicity, or DNA and neural repair on social benefit use among premenopausal breast cancer survivors treated with docetaxel, in a setting with equal access to health care and social benefits.
