Dr. Callahan on Endocrine Therapy in Patients With ER-Positive Breast Cancer

Rena D. Callahan, MD, assistant clinical professor of medicine, University of California, Los Angeles Jonsson Comprehensive Cancer Center, discusses the use of endocrine therapy in patients with estrogen receptor (ER)-positive breast cancer.

Physicians know that triple-negative breast cancer or ER-negative HER2 breast cancer tends to recur early. A patient with those tumor types who reach 5 years can feel confident that they will not have disease recurrence, says Callahan. It is very different for ER-positive disease, notes Callahan.

A study published in the New England Journal of Medicine showed that there was no group thought to be lower risk. This included patients with a node-negative T2 or under lesion; none of these patients had an expected recurrence rate of distant metastases less than 10% in years 5 to 20. Many patients hear about devastating stage IV recurrences and are looking for ways to mitigate that risk. The problem, says Callahan, is that endocrine therapy comes with a lot of side effects. Clinical trials demonstrate a significant dropout rate. Compliance rates 5 years after randomization is only about 65%, and in real life, it is probably a lot less than that, states Callahan.