Characteristics of adverse events of endocrine therapies among older patients with breast cancer

Purpose To clarify the profile of adverse events from endocrine therapies in older patients. Methods We surveyed 15 subjective symptoms including hot flashes, sweating, knuckle stiffness, knee/shoulder joint pain, limb numbness, lethargy, forgetfulness, depressive state, irritated state, genital bleeding, leukorrhea increase, vaginal dryness, bone fracture, and weight gain by a questionnaire among 2044 patients over 55 years old (total number of answered sheets, 8875) and compared the results according to age (56–69 years old vs. ≥ 70 years old) and type of therapy (aromatase inhibitors (AIs) vs. selective estrogen receptor modulators (SERMs)). Among patients 56–69 years old, 6093 and 314 responses were from patients treated with AIs (1477 patients) and SERMs (123 patients), respectively, and 2292 and 176 responses were from those ≥ 70 years old treated with AIs (581 patients) and SERMs (51 patients), respectively. Results In patients ≥ 70 years old, sweating, knuckle stiffness, knee/shoulder joint pain, limb numbness, and lethargy were significantly more frequent/severe with AIs than with SERMs. In those aged 56–69, knuckle stiffness and vaginal dryness were significantly more frequent with AIs than with SERMs, but the opposite occurred for hot flashes, leukorrhea increase, genital bleeding, and weight gain. Conclusions Among patients ≥ 70 years old, many symptoms were significantly more frequent/severe with AIs than with SERMs, compared with those aged 56–69, which suggests a difference in the profile of adverse events according to the type of endocrine therapy and the patient’s age. It is important to consider the benefits and risks of each treatment to optimize endocrine therapy for older patients.