In 10-Year Results from Hormonal Therapy Study, Extended Letrozole Improves Disease-Free Survival

Updated results from the NSABP B-42 trial, presented at the San Antonio Breast Cancer Symposium (SABCS) this week, showed that giving 5 years of the aromatase inhibitor letrozole after 5 years of prior hormonal therapy resulted in a higher rate of disease-free survival in postmenopausal women.

Background

Hormone receptor-positive breast cancers can recur well past 5 years after initial treatment ends. Studies have found that giving hormonal therapy past 5 years may reduce the risk of recurrence, but it’s not clear how much longer people should be given hormonal therapy.

The NSABP B-42 trial compared 5 years on the aromatase inhibitor letrozole to 5 years on placebo in postmenopausal women who had already been given 5 years of hormonal therapy.

Initial results from this study were presented at SABCS in 2016. With only 7 years of follow up at the time, the study showed no statistically significant difference between the letrozole group and the placebo group in terms of disease-free survival. A difference is considered statistically significant if it is not likely a result of chance.

Results

The updated results from NSABP B-42 were presented Thursday, that at 10 years after the study began

• 76.1 percent of people given letrozole did not have a recurrence
• 72.1 percent of people given placebo did not have a recurrence

The difference between the two groups has grown to become statistically significant in the time between reports. This means that 5 years on extended letrozole has resulted in more people living 10 years without breast cancer returning. The study did not find a statistically significant difference in overall survival.

What This Means for You

The question of when and how much to extend hormonal therapy has been a persistent one. People and their doctors want to lower the risk of recurrence where possible, but are increasingly aware that 10 years of treatment is also 10 years of side effects and costs, so it is important that extended treatment shows a significant benefit if providers are to recommend it.

Researchers are cautious in their recommendations, suggesting that providers take into account the risks and benefits of extending hormonal therapy when deciding who should be eligible. Providers should consider how a person has been affected by side effects of hormonal therapy, other health concerns, and features of the cancer itself, including if it is likely to return. Researchers mention new tools that may help make this decision, specifically genomic tests that use information about the tumor’s DNA to predict who is likely to improve their risk of recurrence by staying on hormonal therapy.