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Optimal Duration of Adjuvant Endocrine Therapy Undecided in ER+ Breast Cancer

Caroline Seymour
Published: Tuesday, Jul 10, 2018

Maryann J. Kwa, MD
Maryann J. Kwa, MD
Further biomarker studies are needed to determine which patients may benefit from extended adjuvant endocrine therapy, in an effort to reconcile the high risk of recurrence in patients with estrogen receptor (ER)-positive breast cancer, said Maryann J. Kwa, MD.

Although the risk of distant recurrence continued up to 20 years after follow-up in a meta-analysis of 62,923 women with early-stage, ER-positive breast cancer—pooled from 88 trials from the Early Breast Cancer Trialists’ Collaborative Group—efforts to establish the optimal duration of adjuvant endocrine therapy have been unsuccessful, said Kwa.

“It's a challenge, because patients are concerned about toxicity and that's something that we try to balance with the efficacy of treatment,” Kwa explained.

In an interview during the 2018 OncLive® State of the Science Summit™ on Breast Cancer, Kwa, an instructor in the Department of Medicine, NYU Langone’s Perlmutter Cancer Center, discussed the optimal duration of endocrine therapy in the treatment of patients with early-stage ER-positive breast cancer.

OncLive: What does the landscape of early-stage ER-positive breast cancer look like?

Kwa: The first part of my presentation focused on a meta-analysis that looked at over 60,000 women with early-stage ER-positive breast cancer who had received an initial 5 years of adjuvant endocrine therapy. They followed these women out for up to 20 years to see what the risk of distant recurrence was. The summary of the meta-analysis was published in the New England Journal of Medicine in 2017, and showed that there was a risk of distant recurrence all the way up to the 20-year mark. The risk of distant recurrence was 13% for small tumors and even greater for large tumors and involved lymph nodes.

Afterwards, I discussed the optimal duration of endocrine therapy and whether there is a role for extended adjuvant endocrine therapy. Results of the ABCSG-16 study was presented at the 2017 San Antonio Breast Cancer Symposium and looked at 2 additional years versus 5 years of an extended aromatase inhibitor (AI). The study was performed in Austria. The results showed that there was no overall difference in disease-free survival (DFS) between 2 and 5 years of additional therapy. However, of note, this was a study that involved patients who had smaller tumors that were lower grade and node negative.

I also discussed the highly anticipated, recently reported TAILORx trial. The study was recently discussed at the 2018 ASCO Annual Meeting and looked at intermediate-risk patients who were based on the 21-gene recurrence score. These were patients who had an Oncotype DX Breast Recurrence Score test of 16 to 25. Half of the patients were randomized to receive chemotherapy and endocrine therapy and half were randomized to receive endocrine therapy alone. The study found that there was no difference in DFS between groups. A subgroup analysis looked at women who were 58 years of age or younger and found a small benefit in the women who received both chemotherapy and endocrine therapy.

How do you reconcile the high risk of recurrence in ER-positive breast cancer with compliance rates?

That is a really good question. In one of the studies that I discussed during the presentation, the drop-off rate was much higher in the longer patients who took endocrine therapy versus those who took it for a shorter duration.

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