Utilization of The Breast Cancer Index for HR+ Breast Cancer


Thoughts regarding how the addition of the Breast Cancer Index to the NCCN guidelines for HR+ breast cancer may likely impact extended adjuvant therapy and patient outcomes.

Kristie Kahl: What are the data that are supporting the use of the Breast Cancer Index [BCI] in patients with early hormone receptor–positive breast cancer?

Reshma L. Mahtani, DO: We have extensive clinical evidence of the test validity and utility for the predictive ability of the assay data in around 2000 patients treated in trials, including MA.17R, Trans-aTTom, and the IDEAL trial. Those trials have shown BCI to be a consistent and reproducible predictor of who will benefit from extended endocrine therapy, with about a 65% relative risk reduction shown in patients who have a gene signature that is basically a molecular assessment of the estrogen signaling pathway. The result is very easy, in that it’s very plainly reported as yes or no: yes meaning your patient will benefit from extending therapy, no meaning your patient will not benefit.

Similarly, the prognostic ability of the assay has been validated in a large number of patients—around 2000—including pre- and postmenopausal, node-positive, and node-negative patients. The assay has been shown to provide an individualized risk of distant recurrence from years 5 to 10. This information can help inform the patient as well as the physicians’ perception of their risk of recurrence above and beyond clinical pathology features. I’ve been really surprised to see some of the assumptions that I’ve made in my practice using clinical pathology factors challenged by the results of the BCI, which have shown some patients with N1 disease having a low rate of distant recurrence. At the same time, in some patients who I expected to have a quite good prognosis, their N0 has a higher risk of distant recurrence. This has been very useful in my practice in helping patients make this decision.

Kristie Kahl: To shift gears to the patients, how do you think the addition of the Breast Cancer Index to the NCCN [National Comprehensive Cancer Network] Guidelines will impact patient outcomes?

Reshma L. Mahtani, DO: It has to do with getting the message out that this assay is available and understanding how it can impact decision-making. We need to create awareness in physicians that it is a test that has been endorsed by the NCCN. In that regard, it will have a big impact in that patients who are not really benefiting from endocrine therapy may choose to not continue that treatment and not suffer those adverse effects.

Transcript edited for clarity.

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