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Background: The use of endocrine therapy for early-stage breast cancer, particularly aromatase inhibitor therapy has been associated with an increased risk of osteoporosis and fracture in clinical trials. We sought to validate this observation in real-world practice. Methods: We used health administrative data collected from post-menopausal women (aged ≥66 years) who were diagnosed with breast cancer and started on adjuvant endocrine therapy from 2005 to 2012. Patients were classified by use of either an aromatase inhibitor or tamoxifen and followed until 2017 for a new diagnosis of an osteoporotic fracture. A multivariable analysis using a Cox proportional hazards model was adjusting for age, medical co-morbidities, medication use and duration of endocrine therapy. Results: We identified 12,077 patients of whom 73% were treated with an aromatase inhibitor as compared to 27% with tamoxifen. Our multivariable analysis did not demonstrate any significant difference in the rate of osteoporotic fracture between patients treated with an aromatase inhibitor when compared with tamoxifen [Hazard ratio (HR) = 1.09; 95% confidence interval (CI) = 0.96–1.23, p-value = 0.18]. The 5-year rate of osteoporotic fracture for patients treated with either an aromatase inhibitor or tamoxifen was 7.5% and 6.9%, respectively. A completed sensitivity analysis did observe a decreased risk of fracture associated with tamoxifen usage over time. Conclusion: We could not detect a significant difference in the rate of osteoporotic fracture among patients treated with an aromatase inhibitor versus tamoxifen. Nonetheless, the risk with tamoxifen was numerically lower and significantly decreased when accounting for total duration of endocrine therapy.

Purpose: Adherence to adjuvant endocrine therapy among post-menopausal breast cancer patients is an important survivorship care issue. We explored factors associated with endocrine therapy adherence and survival in a large real-world population-based study. Methods: We used health administrative databases to follow women (aged ≥ 66 years) who were diagnosed with breast cancer and started on adjuvant endocrine therapy from 2005 to 2010. Adherence was measured by medical possession ratio (MPR) and characterized as low (< 39% MPR), intermediate (40–79% MPR), or high (≥ 80% MPR) over a 5-year period. We investigated factors associated with adherence using a multinomial logistic regression model. Factors associated with all-cause mortality (5 years after starting endocrine therapy) were investigated using a multivariable Cox proportional hazards model. Results: We identified 5692 eligible patients starting adjuvant endocrine therapy who had low, intermediate, and high adherence rates of 13% (n = 749), 13% (n = 733), and 74% (n = 4210), respectively. Lower rates of adherence were associated with increased age [low vs. high adherence: odds ratio (OR) 1.03, 95% CI 1.02–1.05 (per year); intermediate vs. high adherence: OR 1.02, 95% CI 1.01–1.04 (per year)]. High adherence was associated with previous use of adjuvant chemotherapy (low versus high adherence OR 0.42, 95% CI 0.30–0.59) and short-term follow-up with a medical oncologist within 4 months of starting endocrine therapy (low versus high adherence OR 0.83, 95% CI 0.69–0.99). Unadjusted analysis showed increased survival among patients with high endocrine therapy adherence. However, an independent association was no longer clearly detected after controlling for confounders. Conclusion: Interventions to improve adjuvant endocrine therapy adherence are warranted. Non-adherence may be a more significant issue among elderly patients. Short-term follow-up visit by a patient's medical oncologist after starting endocrine therapy may help to improve compliance. [ABSTRACT FROM AUTHOR]

The article discusses the usage of aromatase inhibitors in preventing breast cancer. It focuses on the randomized trial, MAP.3, conducted by the National Cancer Institute of Canada Clinical Trials Group (NCIC CTG) which aims to detect reduction in annual incidence of invasive breast cancer (IBC) using exemestane versus placebo. The study concluded that exemestane significantly reduced invasive breast cancers in postmenopausal women.