Purpose TAnDEM is the first randomized phase III study to combine a hormonal agent and trastuzumab without chemotherapy as treatment for human epidermal growth factor receptor 2 (HER2)/hormone receptor–copositive metastatic breast cancer (MBC). Patients and Methods Postmenopausal women with HER2/hormone receptor–copositive MBC were randomly assigned to anastrozole (1 mg/d orally) with or without trastuzumab (4 mg/kg intravenous infusion on day 1, then 2 mg/kg every week) until progression. The primary end point was progression-free survival (PFS) in the intent-to-treat population. Results Overall, 103 patients received trastuzumab plus anastrozole; 104 received anastrozole alone. Patients in the trastuzumab plus anastrozole arm experienced significant improvements in PFS compared with patients receiving anastrozole alone (hazard ratio = 0.63; 95% CI, 0.47 to 0.84; median PFS, 4.8 v 2.4 months; log-rank P = .0016). In patients with centrally confirmed hormone receptor positivity (n = 150), median PFS was 5.6 and 3.8 months in the trastuzumab plus anastrozole and anastrozole alone arms, respectively (log-rank P = .006). Overall survival in the overall and centrally confirmed hormone receptor–positive populations showed no statistically significant treatment difference; however, 70% of patients in the anastrozole alone arm crossed over to receive trastuzumab after progression on anastrozole alone. Incidence of grade 3 and 4 adverse events was 23% and 5%, respectively, in the trastuzumab plus anastrozole arm, and 15% and 1%, respectively, in the anastrozole alone arm; one patient in the combination arm experienced New York Heart Association class II congestive heart failure. Conclusion Trastuzumab plus anastrozole improves outcomes for patients with HER2/hormone receptor–copositive MBC compared with anastrozole alone, although adverse events and serious adverse events were more frequent with the combination.
The prognostic significance of single hormone receptor positive metastatic breast cancer: An analysis of three randomised phase III trials of aromatase inhibitors