Factors Associated With a Greater Risk of Treatment Discontinuation in High-Risk Early Breast Cancer

Sara Tolaney, MD, MPH, Dana-Farber Cancer Institute, Boston, MA, discusses results from the adjuvant abemaciclib trial monarche, analyzing factors that were associated with an increased risk of treatment discontinuation among patients who had high risk hormone receptor positive, HER2-negative, node-positive breast cancer.

Transcript

My name is Sara Tolaney, and I'm a breast medical oncologist at Dana-Farber Cancer Institute. And at ASCO this year, we presented data from the adjuvant abemaciclib trial monarche, and specifically looked at factors that were associated with an increased risk of treatment discontinuation within this trial.

As many of you are probably aware, the monarche study was a trial that looked at patients who had high risk hormone receptor positive, HER2-negative, node-positive breast cancer, and had randomized them to receive endocrine therapy with two years of adjuvant abemaciclib or endocrine therapy alone. And the study had demonstrated that adding abemaciclib to endocrine therapy did result in a significant improvement in invasive disease-free survival, as well as distant relapse-free survival with about a 30% reduction in IDFs events at about 27 months of follow up now. However, we did note that within this trial, approximately 26% of patients did discontinue abemaciclib prior to completing the two year treatment period for reasons other than recurrence.

And so the goal of this particular analysis was to be able to identify patients that are at higher risk of discontinuation, really evaluating the impact of baseline factors, including preexisting comorbidities on the time to discontinuation for abemaciclib. And so the way the study was structured was that we initially looked at various baseline factors that we thought could be attributed to early discontinuation and proceeded with a univariate variable selection followed by a stepwise variable selection, and specifically looked at the impact of these factors as independent prognostic factors for discontinuation at six months, 12 months and 24 months within each subgroup.

And what we found with multivariate analysis was that the factors that were associated with early discontinuation included geographic region, menopausal status, age, baseline, performance status, number of positive nodes, and number of unique existing comorbidities. And for me, some of these factors seemed like common sense for factors that may be associated with higher rates of discontinuation, such as things like older age, worse performance status, multiple comorbidities.

But I think some of the factors were somewhat surprising. One being people who had fewer lymph nodes involved tend to have higher rates of discontinuation, and one could sort of rationalize this thinking that people of higher risk disease may have a higher threshold towards discontinuation. But I think other factors that I was a bit surprised by included geographic region, where we found that people of north American and European descent were more likely to have early discontinuation compared to patients, for example, from Asian countries.

So, I think overall this analysis did suggest that there are factors that can help us better understand which patients may be at higher risk for early discontinuation of abemaciclib. And I think what this really suggests is that we need to think about patients who may have these risk factors and more closely monitor these patients and make sure that we are proactively recommending supportive measures to help them through their treatment, such as things like dose modifications use of antidiarrhea therapy. And hopefully these measures will help retain patients on abemaciclib therapy.

Thank you so much for listening.