BCI testing is reshaping treatment decisions for early-stage HR+ breast cancer patients by helping guide personalized endocrine therapy choices.

By Andy Lundin

A new study found that a significant proportion of early-stage hormone receptor-positive (HR+) breast cancer patients may be making the wrong endocrine therapy treatment decisions, and that breast cancer index (BCI) testing can guide patient decisions on extending this type of hormone therapy.

The decision of whether HR+ breast cancer patients should extend endocrine therapy to reduce the risk of cancer recurrence is multilayered. On the one hand, this method of hormone therapy—commonly taken for five years—can reduce the risk of cancer recurrence by 40% and up to 75% for some people1. On the other hand, if a patient intends to extend this therapy, there is a chance they may experience potential side effects and toxicities, which are associated with longer anti-estrogen therapy.

Further reading: New Test Predicts Recurrence Rate in Early-Stage Invasive Breast Cancer Patients

Changing Perspectives on Extending Endocrine Therapy

The new study, published by Hologic and its subsidiary, Biotheranostics, looked at how BCI testing notably influenced treatment decisions regarding endocrine therapy for early-stage HR+ patients. Indeed, 40% of physician treatment recommendations related to extended endocrine therapy changed following BCI testing2. Of the physician treatment decisions that changed:

Tara Sanft, MD
  • 63% went from a yes to a no recommendation for extended anti-estrogen therapy.
  • The remaining 37% changed from a no to a yes recommendation.

“While previous studies have demonstrated that some women with early-stage HR+ breast cancer may reduce their risk of recurrence with extended endocrine therapy, most women do not benefit,” says Tara Sanft, MD, primary author, associate professor of Medicine at Yale School of Medicine and chief patient experience officer at Smilow Cancer Hospital. “Additionally, this therapy is often accompanied by the potential for adverse events such as bone and cardiovascular toxicities, endometrial cancer, and other side effects that impair quality of life. The Breast Cancer Index test can tell us both what a patient’s risk of recurrence is and if continuing endocrine therapy beyond 5 years is likely to help reduce that risk.”

The BCI Registry Study

Patients and physicians included in this study are participants in the BCI Registry Study, which is a prospective, large-scale, multi-center study that investigates long-term clinical outcomes, decision impact, and medication adherence in patients with early-stage HR+ breast cancer receiving BCI testing as part of routine clinical care.

The Breast Cancer Index is a genomic test recognized by the American Society of Clinical Oncology (ASCO) and the NCCN Clinical Practice Guidelines in Oncology to predict extended endocrine therapy benefits, Hologic says.

“Extended endocrine therapy can help reduce the risk of recurrence for some women, but it can also impact a patient’s quality of life,” says Sanft. “As healthcare providers, it is important that we gather all of the information we can to help us make the best treatment recommendation for each individual patient.”

Andy Lundin is the associate editor of CLP.


  1. Orr L. Hot Flashes, Vaginal Dryness: Is Endocrine Therapy Worth It for Breast Cancer? https://www.urmc.rochester.edu/news/story/hot-flashes-vaginal-dryness-is-endocrine-therapy-worth-it-for-breast-cancer
  2. Sanft T, Wong J, O’Neal B, et al. Impact of the Breast Cancer Index for Extended Endocrine Decision-Making: First Results of the Prospective BCI Registry Study. Journal of The National Comprehensive Cancer Network. Published online March 04, 2024. doi:10.6004/jnccn.2023.7087