*Article* **Adherence to Adjuvant Endocrine Therapy in Breast Cancer Patients**

**Roberta Rosso, Marta D'Alonzo, Valentina Elisabetta Bounous \*, Silvia Actis, Isabella Cipullo, Elena Salerno and Nicoletta Biglia**

> Division of Gynecology and Obstetrics, Department of Surgical Sciences, School of Medicine, University of Turin, 10100 Turin, Italy

**\*** Correspondence: valentinaelisabetta.bounous@unito.it

**Abstract:** Background: Adjuvant endocrine therapy (AET) reduces breast cancer recurrence and mortality of women with hormone-receptor-positive tumors, but poor adherence remains a significant problem. The aim of this study was to analyze AET side effects and their impact on adherence to treatment. Methods: A total of 373 breast cancer patients treated with AET filled out a specific questionnaire during their follow up visits at the Breast Unit of our Centre. Results: Side effects were reported by 81% of patients, 84% of those taking tamoxifen and 80% of those taking aromatase inhibitors (AIs). The most common side effect in the tamoxifen group was hot flashes (55.6%), while in the AI group it was arthralgia (60.6%). The addition of GnRH agonists to both tamoxifen and AI significantly worsened all menopausal symptoms. Overall, 12% of patients definitively discontinued AET due to side effects, 6.4% during the first 5 years and 24% during extended therapy. Patients who had previously received chemotherapy or radiotherapy reported a significantly lower discontinuation rate. Conclusions: AET side effects represent a significant problem in breast cancer survivors leading to irregular assumption and discontinuation of therapy. Adherence to AET may be improved by trustful patient–physician communication and a good-quality care network.

**Keywords:** breast cancer; adjuvant endocrine therapy; adherence to treatment; side effects; tamoxifen; aromatase inhibitors; GnRH agonist; questionnaire
