Purpose Aromatase inhibitors (AIs) are effective for treatment of hormone receptor–positive breast cancer, but adherence and persistence with therapy are poor. Predictors of treatment discontinuation are not clearly defined. It is unknown whether patients with intolerable toxicity from one AI are able to tolerate another. Patients and Methods Women with early-stage breast cancer initiating AI therapy were enrolled onto a multicenter, prospective, open-label randomized trial of exemestane versus letrozole. Patients completed symptom questionnaires at baseline and serially during therapy. Patients who developed AI-associated intolerable symptoms and discontinued treatment were given the option to switch to the other study AI after a 2- to 8-week washout period. Results Of the 503 enrolled women, 32.4% discontinued initial AI therapy within 2 years because of adverse effects; 24.3% discontinued specifically because of musculoskeletal symptoms. Median time to treatment discontinuation as a result of any symptom was 6.1 months (range, 0.1 to 21.2 months) and was significantly shorter in patients randomly assigned to exemestane (hazard ratio [HR], 1.5; 95% CI, 1.1 to 2.1; P = .02). Younger age and taxane-based chemotherapy were associated with higher likelihood of treatment discontinuation (HR, 1.4; 95% CI, 1.02 to 1.9; P = .04; and HR, 1.9; 95% CI, 1.00 to 3.6; P = .048, respectively). Of the 83 patients who chose to switch to the second AI, 38.6% continued the alternate AI for a median of 13.7 months. Conclusion Premature discontinuation of initial AI therapy as a result of symptoms is common, although more than one third of patients may be able to tolerate a different AI medication. Additional research is needed to identify predictive tools and interventions for AI-associated treatment-emergent symptoms.

Using data obtained from an inception cohort of 841 patients aged 65 or older newly diagnosed with breast, colon, lung, or prostate cancer, and observed at 6-8, 12-16, 24-30, and 52 weeks, three questions related to patients' experiences with pain and fatigue were posed. First, how do numbers of patients reporting neither pain nor fatigue, either symptom, or both change during the observation year? Second, did number of comorbid conditions, site and stage of cancer, treatment modalities, symptom management medication, and time affect the presence of these two symptoms? Third, do pain and fatigue predict the numbers of co-occurring other symptoms? Findings indicate that during the year patients improved with respect to their reports of pain and/or fatigue. Stage, more comorbidity, and lung cancer were related to both pain and fatigue. Chemotherapy was related to reports of fatigue, but did not have an extended effect on fatigue.