1616O5-year adherence to adjuvant endocrine therapy among women with breast cancer: A nationwide study using group-based trajectory modeling

Abstract Background Adjuvant endocrine therapy (AET) is an oral medication prescribed to women with hormone-sensitive breast cancer (BC). AET is recommended daily for at least 5 years to reduce recurrence and mortality risks. Studies showed that a high proportion of women do not take daily or do not persist with AET for the recommended duration. The objectives of this study were to identify: 1) AET adherence trajectories for the 5 years following AET initiation among women diagnosed with non-metastatic BC and 2) factors associated with these trajectories. Methods We used data from the French Cohorte Cancer which includes data on hospitalizations, ambulatory care and medication claims for all cancer cases diagnosed in metropolitan France (SNDS database) . Women diagnosed with a first non-metastatic BC in 2011 and who had ≥1 AET claim in the 12 months after surgery were included in this study. For each woman, we estimated the proportion of days covered (PDC) by an AET for each month in the 5 years after AET initiation. Monthly PDCs were used to model AET adherence trajectories using Group-based trajectory modeling (GBTM). Statistical criteria were used to select the number of trajectories and evaluate the adequacy of the selected model. Factors associated with trajectories were identified using multinomial logistic regressions comparing. Results 33 260 women were included. A 6-trajectory model wasselected: 1) 6.6% stopped the treatment by the end of the first year of treatment, 2) 5.7% declined adherence around half-term treatment 3) 6.3% after around 3 years, 4) and 8.3% after 4 years, 5) adherence varied between 50% and 60% without ever stopping for 4.3% of women and 6) 68.8% had an optimal adherence over the whole duration of treatment. Factors associated with trajectories included age, switch of molecule of AET during the treatment and the type of surgery. Conclusions To our knowledge, this is the first nationwide study to describe 5-year AET adherence trajectories. By identifying the timing of AET decline and/or cessation and factors associated with longitudinal adherence patterns, results could guide the development of interventions aimed at supporting women having an AET. Legal entity responsible for the study Institut National du Cancer (INCa). Funding INCa. Disclosure All authors have declared no conflicts of interest.