Administering endocrine therapy for 5 years significantly reduces recurrence rates during and after treatment for patients with early-stage, ER-positive breast cancer. Continuing to administer therapy after 5 years may offer further protection against recurrence, but is associated with additional side effects. Further research on the absolute risk of subsequent distant recurrence if therapy stops at 5 years would help physicians determine whether or not to extend treatment.
Daniel F Hayes, MD, Stuart B Padnos Professor of Breast Cancer Research, University of Michigan Comprehensive Cancer Center, and colleagues conducted a meta-analysis of the results of ER-positive breast cancer trials that tested endocrine therapy. A total of 88 trials involving 62,923 patients were analyzed. Kaplan-Meier and Cox regression analyses were utilized to evaluate the associations between tumor diameter and nodal status (TN), tumor grade, and other factors with patient outcomes during the period from 5 to 20 years after endocrine therapy had stopped.
Researchers found that breast cancer recurrence occurred steadily throughout the 5 to 20-year period. Risk of distant recurrence was significantly associated with original TN status. Among patients with stage T1 cancer, risk of distant recurrence was 13% with no nodal involvement, 20% with one to three nodes involved, and 34% with four to nine nodes involved. Similarly, patients with stage T2 disease were subject to risks of 19%, 26%, and 41%, respectively.
Furthermore, Dr Hayes and colleagues found that during the study period, the absolute risk of distant recurrence among patients with stage T1 disease and no nodal involvement was 10% for low-grade cancer, 13% for moderate-grade cancer, and 17% for high-grade cancer. Corresponding risks of any recurrence or a contralateral breast cancer were 17%, 22%, and 26%, respectively.
Researchers concluded that from 5 to 20 years after endocrine therapy stopped for patients with early-stage, ER-positive breast cancer, recurrence continued to occur steadily. Risk of distant recurrence was significantly correlated with the original TN status, with risks ranging from 10% to 41% depending on TN status and tumor grade, they wrote.
"These data can be used by patients and their health care providers as they consider whether to continue taking anti-estrogen therapy beyond five years, weighed against side effects and toxicity of the therapies," Dr Hayes commented (November 8, 2017).—Zachary Bessette