Continue Medication After 5 Years of Breast Cancer Treatment? Breast Cancer Index Changed 41.7% of Recommendations

A study found that the Breast Cancer Index test can help determine whether patients with early-stage hormone receptor-positive breast cancer should continue taking medication after completing 5 years of adjuvant endocrine therapy.

According to the final analysis of the Breast Cancer Index registry study, published on the 1st (local time) in the American Medical Association journal JAMA Network Open, the test changed treatment recommendations for more than 4 in 10 physicians and increased physicians’ and patients’ confidence in their decisions.

The researchers analyzed 2,900 women with early-stage hormone receptor-positive breast cancer who had completed 4 to 7 years of adjuvant endocrine therapy and had not experienced a recurrence. The Breast Cancer Index consists of a prognostic model and a predictive model: The prognostic model assesses the risk of late distant recurrence, while the predictive model assesses the likelihood of benefit from extended endocrine therapy.

Test results classified 1,100 patients as having a high likelihood of benefit from extended endocrine therapy and 1,800 as having a low likelihood. Prognostic risk was low for 1,348 patients and high for 1,552.

Changes in physicians’ recommendations were most pronounced. Before testing, 55.4% of physicians recommended extended endocrine therapy; after testing, that figure fell to 42.6%, and 41.7% changed their recommendation.

The proportion of recommendations for patients with a high likelihood of benefit rose from 61.0% to 92.2%, while the proportion of recommendations against treatment for patients with a low likelihood of benefit increased from 47.6% to 87.6%.

When prognostic and predictive results were considered together, the proportion of recommendations against treatment for patients with both low risk and a low likelihood of benefit rose from 54.5% to 93.2%. The proportion of recommendations for treatment for patients with both high risk and a high likelihood of benefit increased from 63.5% to 96.3%.

The proportion of physicians reporting high confidence rose from 64.1% to 88.7%, and 43.8% said they felt more confident.

Changes among patients were also pronounced. Preference for extended endocrine therapy fell from 75.8% to 53.6%, and 51.0% changed their preference. The proportion of patients reporting high comfort rose from 71.6% to 86.0%.

When physicians’ recommendations did not align with the Breast Cancer Index predictions, prognostic scores provided additional context. Patients with a high likelihood of benefit who were not recommended treatment tended to have smaller tumors and lower prognostic risk, while patients with a low likelihood of benefit who were recommended treatment tended to be younger, have larger tumors, and have higher rates of lymph node involvement and chemotherapy.

The researchers concluded that the Breast Cancer Index can help shift decisions about extended endocrine therapy from a uniform approach to individualized choices, supporting recommendations for patients more likely to benefit while helping avoid unnecessary long-term medication use.