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Expert Addresses Optimal Use of Endocrine Therapy in HR+ Breast Cancer

Caroline Seymour
Published: Wednesday, May 09, 2018

Rena D. Callahan, MD
Rena D. Callahan, MD
Results of a meta-analysis revealed that the use of endocrine therapy for 5 years significantly reduced recurrence rates in women with early-stage, estrogen receptor (ER)-positive breast cancer with additive benefits that extend beyond 5 years. However, the apparent benefit, notes Rena D. Callahan, MD, must be weighed against adverse events (AEs).

on Breast Cancer, Callahan, an assistant clinical professor of medicine at the University of California, Los Angeles Jonsson Comprehensive Cancer Center, discussed controversies in the management of early-stage HR-positive breast cancer and neoadjuvant trial designs for these patients.

OncLive: Please provide an overview of your presentation.

Callahan: It was my pleasure to discuss the optimal duration of endocrine therapy, because this is a hot topic that affects a lot of our patients. Most of our patients have early-stage and ER-positive disease, so this is very relevant to them. Over the past several years, we’ve been toying with the idea of whether or not we can get more of a good thing. Physicians know that more aggressive cancers, such as triple-negative breast cancer or ER-negative, HER2-positive breast cancer, tend to recur early. A patient with those tumor types who reaches 5 years can feel confident that they will not have disease recurrence. It is very different for ER-positive disease.

 by Dr Hongchao Pan 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 is that endocrine therapy comes with a lot of AEs.

How does 2 years of additional endocrine therapy compare with 5 years?

A few different studies have looked at 5 years of an extended aromatase inhibitor [beyond the initial 5 years] versus a shorter duration. At the 2017 San Antonio Breast Cancer Symposium, Dr Michael Gnant presented the ABCSG-16 study. The study showed no difference in DFS whether [a patient] took an aromatase inhibitor for an additional 5 years or 2 years. There was no overall survival benefit, so at this point it doesn't seem worth it to continue because of increased toxicity— specifically bone-related fractures and no benefit in survival.

That doesn’t necessarily mean that there isn't a patient who would benefit from 5 years over 2 years. That study [enrolled] mostly node-negative patients with smaller tumors; these are pathologic factors that are associated with a lower overall risk of recurrence.

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