The Breast Cancer Index (BCI) is a test that analyzes a breast cancer patient’s genes. In women with estrogen receptor-positive (ER-positive) breast cancer, BCI predicts risk of recurrence beyond five years and predicts how likely a patient is to respond to hormone therapy. This is a powerful tool for clinicians and provides important information for patients because it helps to individualize treatment.
The Breast Cancer Index & Disease Management
For many years, most ER-positive breast cancer patients were treated with a similar combination of systemic therapy, chemotherapy and hormone therapy. It became the standard of care to treat these women for five years with Tamoxifen following chemotherapy.
Although survival at five years is sometimes used as a benchmark to determine whether a patient has ‘beat’ cancer, it is used somewhat arbitrarily. In women with ER-positive breast cancer, more than one-half of recurrences occur and more than two-thirds of deaths occur after five years.
More recently, several trials have shown that ER-positive patients can benefit from treatment with Tamoxifen or therapy beyond five years. With this knowledge, many oncologists offered their patients the option of continuing therapy for 10 years. However, only about 1 in 20 of these patients would benefit from lengthier courses of treatment. More than one-half would suffer side effects, such as hot flashes or sexual dysfunction, or even more serious complications, such as uterine cancer.
Improving Individualized Treatment
With BCI and other similar tests, we are able to better identify which patients can benefit. If a woman receives a low-risk score on BCI, she will be unlikely to benefit from lengthier course of treatment. By better understanding risk-benefit tradeoffs, women and their physicians can more confidently choose treatments that don’t sacrifice quality-of-life.
To make informed decisions about treatment, women and their physicians need accurate information about their individual cancers. Our goal should be to provide care than is neither under-treatment nor over-treatment. Tests like BCI help us to offer individualized care that can achieve this goal. As our understanding of breast cancer genomics continues to improve, we will see new therapies that further improve treatment options.