Adherence to adjuvant hormonal therapy in localised breast cancer

Hormonal therapies are the cornerstone of systemic adjuvant treatment of oestrogen receptor (ER) positive breast cancer. The full benefit of this treatment is obtained with long-term adherence. However, discontinuation of hormonal therapy is common. Factors associated with non-compliance to therapy are complex and worth of detailed evaluation.A retrospective analysis of medical records of 284 early ER-positive breast cancer patients prescribed adjuvant hormonal therapy during a 5-year period in a single centre was undertaken. Characteristics of the patients and their disease as well as adherence to therapy and continuation at 1 and 3 years were recorded. The group of patients that were on treatment at 3 years and the group that had discontinued therapy before 3 years were compared to identify differences predicting lack of adherence.The discontinuation rate of hormonal therapy at 1 year was 13%, and the discontinuation rate at 3 years was 21.2%. Patient age and menopause status were not associated with hormone therapy adherence at 3 years. The type of hormonal therapy (aromatase inhibitor or tamoxifen) was also not associated with adherence. In contrast, patients that received adjuvant chemotherapy before starting hormonal therapy had a higher adherence to hormonal therapy (86.9% at 3 years vs. 75.7% in patients that had not received adjuvant chemotherapy, χ2 p = 0.04). Among co-morbidities, patients with a concomitant diagnosis of psychiatric disease at the time of breast cancer diagnosis were at increased risk of hormone therapy non-adherence. Progression-free survival and overall survival were inferior in the non-adherent group compared with the patients who continued their hormonal therapy at 3 years.Adjuvant chemotherapy is associated with better subsequent adherence to hormonal therapy in early breast cancer patients. On the other hand, psychiatric co-morbidities are associated with worse adherence. De-escalation of adjuvant therapy guided by genomic tests leads to a significant percentage of early ER-positive breast cancer patients not receiving chemotherapy. Non-adherence to hormonal therapy would leave a subset of these patients with no adjuvant systemic therapy. The current results will guide efforts to increase compliance to hormonal therapies in specific groups of patients.