62O_PR Non-adherence to adjuvant endocrine treatment and its determinants among early stage breast cancer patients

Abstract

Background Non-adherence to adjuvant endocrine treatment (ET) among breast cancer patients has been associated with worse prognosis. We sought to identify factors affecting non-adherence to ET, taking into account determinants at baseline and followup. Methods From linkage between Swedish national registers, we identified all women diagnosed with stage I-III, ER-positive breast cancer in Stockholm-Gotland, Uppsala- O€rebroand NorthernSwedenbetween 2006 and 2009.A total of 4,413 women who had at least one dispensation of tamoxifen or aromatase inhibitors (AIs) and 5 years of follow-up were included in the analysis. A medical possession ratio (MPR) of < 80% was used to define non-adherents. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) of non-adherence to ET. Results During follow-up, 1,131 (25.6%) women became non-adherents. The following determinants of non-adherence were identified: age, marital status, region of diagnosis, private hospital, tumour size, lymph node metastasis, tumour grade, HER2 status, type of surgery, adjuvant chemotherapy, type of ET, pre-diagnostic hormone replacement therapy, the use of symptom-relieving drugs at baseline and during follow-up, baseline scores and any increase in Charlson co-morbidity index (CCI). In multivariable analysis, non-adherence was only associated with younger age (OR: 0.67; 95%CI: 0.50- 0.90and0.66; 0.48-0.92 forage50-65 and65+ comparedto < 50, respectively), marital status(OR:1.40;95%CI:1.23-1.60forsingle/divorced/widowedcomparedtomarried women),socioeconomicstatus(OR:1.17;95%CI:1.00-1.37and1.60;1.16-2.21for white collar and being unemployed compared to blue collar workers, respectively), and pre-diagnostic use ofhormone replacementtherapy(OR: 1.57; 95%CI: 1.28-1.93). Conclusions Our study identifies socioeconomic subgroups with increased risk ofnon- adherence that may be of use when measures for improving adherence are tested. Women with pre-diagnosticuseofHRT mayrepresentabiologicalsubsetwith a disposition for side effects from ET. Legal entity responsible for the study King's College London Funding King's College London Disclosure All authors have declared no conflicts ofinterest.