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Effect of 5 Years’ Endocrine Therapy on Breast Cancer Recurrence

By: Celeste L. Dixon
Posted: Monday, November 27, 2017

An international team has found that the recurrence risk of estrogen receptor–positive breast cancer, even after 5 years’ endocrine therapy, relates directly to the initial cancer’s size, characteristics, and number of affected lymph nodes. Throughout a study period from 5 to 20 years, breast cancer recurrences continued at a steady pace. The findings are “remarkable,” said lead author Hongchao Pan, PhD, of the University of Oxford, in a press release.

The investigators, members of the Early Breast Cancer Trialists’ Collaborative Group, analyzed data from 88 clinical trials that followed almost 63,000 women with estrogen receptor–positive breast cancer up to 20 years after diagnosis. All had taken tamoxifen or an aromatase inhibitor for 5 years and were cancer-free at therapy’s end.

The women with the largest tumors at diagnosis, whose cancer had spread to four or more lymph nodes, experienced a 41% risk of distant cancer recurrence in the 15 years after ending endocrine therapy. The risk was lowest, 10%, in women with the smallest tumors and no affected nodes. Recurrence sites included the bone, liver, lung, and contralateral breast.

However, co-lead author Richard Gray, MSc, also of the University of Oxford, noted that women diagnosed today may benefit from better treatments than those available 2 decades ago. “Recurrence rates will be somewhat lower for women diagnosed more recently,” he said in the press release. Nonetheless, the findings suggest that women with estrogen receptor–positive breast cancer consider taking antiestrogen therapy past the 5-year mark, said the authors, whose work was published in The New England Journal of Medicine.