Nearly half of older men with hormone-positive breast cancer discontinue adjuvant endocrine therapy within 5 years, with a significant rate of nonadherence among those who continue therapy. These findings were published in the journal Cancer.

Adjuvant tamoxifen is proven to reduce the risk of systemic recurrence or a contralateral breast cancer by as much as 50% in women with early-stage disease. Tamoxifen also is proven efficacious in men with metastatic breast cancer, and therefore, has been adopted as standard treatment for men with early-stage breast cancer.

Some studies indicate that men are likely to discontinue endocrine therapy. However, men with breast cancer only account for 1% of cases, and men are rarely included in clinical trials. Information and management of the disease in men is based on studies that enrolled women. Therefore, a team of researchers at the University of Texas MD Anderson Cancer Center sought to determine the incidence of tamoxifen discontinuation and medication adherence among men with early-stage hormone-positive breast cancer.

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A cohort of 451 men, median age 75 years, with stage I to III hormone-receptor positive breast cancer between 2007 and 2013, were identified from the Surveillance, Epidemiology and End Results – Medicare database for this study. All the patients received tamoxifen within 1 year of diagnosis and had Part D coverage within 12 months of their first prescription.

Predictors of adherence within 1 year of the first tamoxifen prescription included age 76 to 80 years at diagnosis and residence in an urban or suburban area. Men older than 80 at diagnosis were at higher risk of tamoxifen discontinuation, as were men with a Charlson comorbidity score of 2 or higher.

Study results showed that up to 15.8% of older men discontinued their tamoxifen within 1 year after the first prescription. At 2 years, the discontinuation rate in this cohort was 24.3%; and 31.3% at 3 years, 36.9% at 4 years, and 48.3% at 5 years.

“Adherence declines as time progresses, and by 5 years, almost half of the men prescribed adjuvant tamoxifen have stopped taking it, which could increase risk of recurrence and death from breast cancer,” the researchers reported.

This information highlights an ongoing issue, and should prompt oncology clinicians to be mindful of encouraging their male patients with breast cancer to stick with their endocrine therapy regimen. The researchers also called for further studies into the root causes of endocrine therapy discontinuation and risk factors for nonadherence.

Disclosures: Some authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.


Oke O, Niu J, Chavez-MacGregor M, Zhao H, Giordano SH. Adjuvant tamoxifen adherence in men with early-stage breast cancer. Cancer. 2022;128(1):59-64. doi:10.1002/cncr.33899