Information on toxic effects was collected for 678 patients (332 in group 1 and 346 in group 2); information was not collected for the 6 patients who received no study treatment and was incomplete for 10 patients. Only 15 patients discontinued the study treatment early owing to toxic effects (4 in group 1 and 11 in group 2, P = 0.12). In general, the toxic effects were mild and did not differ significantly in grade between the two groups (see Table 1 in the Supplementary Appen-dix, available at NEJM.org). Toxic effects of grade 3 or higher were observed in 42 patients who received anastrozole alone (12.7%) and in 51 patients who received combination therapy (14.7%) (P = 0.44). The most common grade 3 toxic effects were musculoskeletal pain (2.8%), influenza-like symptoms (2.4%), gastrointestinal disturbances (1.5%), and hematologic effects (1.5%).