Endocrine treatment and incidence of relapse in women with oestrogen receptor-positive breast cancer in Europe: a population-based study

Abstract

Purpose Endocrine therapy (ET) is the mainstream adjuvant treatment for ER-positive breast cancer (BC). We analysed 9293 ER-positive BC patients diagnosed in nine European countries in 2009–2013 to investigate how comorbidities at diagnosis, age, stage and subtype affected ET use over time, and relapse. Methods Adjusted odds ratios (ORs) and 95% confidence intervals (95%CIs) of receiving ET were estimated according to Charlson comorbidity, age, stage and subtype using logistic regression. The 2-year cumulative incidence and adjusted sub-hazard ratios (SHRs) of relapse were estimated using competing risk analysis, with all-cause death as the competing event. The z-test was used to assess differences in the proportion of patients receiving ET in 1996–1998 and 2009–2013. Results Ninety percent of the patients started adjuvant ET, range 96% (Belgium, Estonia, Slovenia, Spain)—75% (Switzerland). ORs of starting ET were lower for women aged > 75 years, with severe comorbidities, or luminal B HER2-positive cancer. The factors independently increasing the risk of relapse were: not receiving ET (SHR 2.26, 95%CI 1.02–5.03); severe comorbidity (SHR 1.94, 95%CI 1.06–3.55); luminal B, either HER2 negative (SHR 3.06, 95%CI 1.61–5.79) or positive (SHR 3.10, 95%CI 1.36–7.07); stage II (SHR 3.20, 95%CI 1.56–6.57) or stage III (SHR 7.41, 95%CI 3.48–15.73). ET use increased significantly but differently across countries from 51–85% in 1996–1998 to 86–96% in 2009–2013. Conclusions ER-positive BC patients in Europe are increasingly prescribed ET but between-country disparities persist. Older women and women with severe comorbidity less frequently receive ET. ET omission and severe comorbidity independently predict early disease relapse.