Assessing the Benefits of Endocrine Therapy in Breast Cancer

Naomi Dempsey, MD, breast medical oncologist at the Miami Cancer Institute, discusses her poster for the 2023 San Antonio Breast Cancer Symposium, "Correlative analysis of Breast Cancer Index with CTS5 for prediction of extended endocrine benefit in the BCI Registry study." The study identifies that results of the Breast Cancer Index assay do not necessarily correlate with the CTS5 calculator to predict how well a patient with breast cancer will respond to endocrine therapy to prevent disease recurrence. In this interview, Dempsey talks about her poster and the implications this study's finding have on patient care.

Transcription:

My name is Naomi Dempsey, and I'm a breast medical oncologist from the Miami Cancer Institute in Miami, Florida. And I'm here today to talk about my poster for the San Antonio Breast Cancer Symposium 2023 entitled, "Correlative analysis of Breast Cancer Index with CTS5 for prediction of extended endocrine benefit in the BCI Registry study."

Patients with hormone receptor-positive, HER2-negative early breast cancer have risk of late distant recurrence. And as clinicians, we are always trying to determine who is that patient who's going to benefit from extended endocrine therapy beyond 5 years versus those who will not. And historically, that decision was made based on things like large tumor size, positive lymph nodes, high tumor grade. And in more recent years, many clinicians have started using the Breast Cancer Index to help us make these decisions. The Breast Cancer Index is a genomic assay that gives both prognostic information regarding the risk of late recurrence, but also predictive information that tells us about whether or not an individual patient will benefit from extended endocrine therapy. So the idea behind this poster was actually seeing how well do those classic clinical pathologic risk factors correlate with the Breast Cancer Index prediction of increased benefit from extended endocrine therapy. In order to do this, we looked at women in the Breast Cancer Index Registry study, which is a registry of women with early hormone receptor-positive, HER2-negative breast cancer, who had undergone testing with the Breast Cancer Index, and had received adjuvant endocrine therapy. And we looked at some of these clinical risk factors in these women, as well as looking at their Breast Cancer Index information. And so in order to put together all of those risk factors, we used the clinical treatment score, abbreviated as CTS5, that gives the prognostic information regarding those clinical pathologic risk factors, and comparative to the predictive portion of the Breast Cancer Index to see how well those correlated meaning can we just use these clinical risk factors like large tumor size, node positivity, high grade to predict who will benefit from endocrine therapy. And when we looked at these 2 variables together, the correlation was 0.18, meaning very poor correlation between the CTS5 and the Breast Cancer Index predictive result. And interestingly, when we looked at the patients specifically, who would have been considered high-risk with the CTS5 score, about half of those patients were predicted by breast cancer index to have a benefit from extended endocrine therapy. But fully another half would not have benefited from extended and current therapy.

Patients are generally pretty comfortable with the idea of taking 5 years of adjuvant endocrine therapy. That is kind of considered the standard. But there are certain patients who will benefit from 10 years of endocrine therapy, and it's really important to determine who are those patients. Nobody wants to be taking a medication that they don't need. And many women are going to experience side effects from endocrine therapy, the ones that are not dangerous, but are uncomfortable, such as hot flashes and joint pain, but also ones that maybe they don't feel, such as a decrease in their bone density or a very small increase in cardiovascular risk, which needs to be integrated into their overall cardiovascular risk. So even for the women at 5 years, who say, I don't have any side effects, I feel fine, why not go to 10? Well, there may be side effects that they are having that they are not feeling. And thus it's really important to determine who will actually benefit. And whereas in the past, we all just kind of said, well, if you've got a positive lymph node, if you have a larger tumor, you should take 10 years of of adjuvant endocrine therapy. The results from my poster really suggest that a more genomically directed approach, using an assay such as Breast Cancer Index can help us to make sure that we're giving the right duration of therapy to the right patient.