Palbociclib regimens extend survival for Black, Hispanic women with advanced breast cancer
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The addition of palbociclib to endocrine therapy prolonged survival for Black and Hispanic women with hormone receptor-positive, HER2-negative metastatic breast cancer, according to results presented at San Antonio Breast Cancer Symposium.
The findings support the continued use of palbociclib plus endocrine therapy for Black and Hispanic patients with hormone receptor-positive HER2-negative advanced breast cancer, according to the investigators.
“We assess many different factors in clinical trials, but one thing we often don’t address is heterogeneity in the patient population. There are different genomic makeups, comorbidities and susceptibilities to toxicities — and potentially different efficacies, as well — among different populations ,” Hope S. Rugo, MD, professor of medicine and director of breast oncology and clinical trials education at University of California, San Francisco, told Healio. “When we are looking at adding targeting agents to treatments with efficacy and toxicity that may be impacted significantly by metabolic differences, it is critical to examine the differences in populations and, specifically, minority populations. This serves many purposes.”
For example, it gives oncologists the confidence when treating patients of different backgrounds, Rugo added
“It also gives confidence to our patients that we have data that represent them because it is very difficult to trust data that does not represent you,” she said. “When looking at clinical trial participation, minority participation is quite low, and one of the ways that we can counter this long-term is by representing minorities in our clinical trials.”
Data on treatment patterns and effectiveness of palbociclib (Ibrance, Pfizer) among minority patients with metastatic breast cancer are limited.
Rugo and colleagues conducted a post-hoc analysis that included 113 Black and Hispanic patients with hormone receptor-positive, HER2-negative metastatic breast cancer included in the PALOMA-1, PALOMA-2 and PALOMA-3 trials.
In PALOMA-1 and PALOMA-2, postmenopausal women received letrozole plus either palbociclib or placebo as first-line therapy. In PALOMA-3, both premenopausal and postmenopausal women who had progressed on prior endocrine therapy received fulvestrant plus either palbociclib or placebo.
Median PFS served as the primary endpoint. Secondary endpoints included OS and safety.
In PALOMA-2, 9.8% (n = 65) of the population self-identified as Black or Hispanic. Forty-seven received palbociclib-letrozole and 18 received placebo-letrozole.
In PALOMA-3, 9.2% (n = 48) of patients self-identified as Black or Hispanic. Twenty-nine received palbociclib-fulvestrant and 19 received placebo-fulvestrant.
Results of PALOMA-2 showed higher median PFS among Black or Hispanic patients with the palbociclib combination (27.4 months vs. 13.8 months; HR = 0.61; 95% CI, 0.31-1.2). Median OS data had not yet matured.
In PALOMA-3, results showed longer median PFS among Black or Hispanic patients assigned palbociclib-fulvestrant (11.1 months vs. 1.9 months; HR = 0.56; 95% CI, 0.28-1.14). Researchers also reported longer median OS with the palbociclib regimen (35.6 months vs. 21 months; HR = 0.48; 95% CI, 0.23-0.97).
Results of pooled analyses of Black and Hispanic patients included in the PALOMA-1, PALOMA-2 and PALOMA-3 trials showed the most common grade 3 or grade 4 adverse events in the palbociclib plus endocrine therapy groups included neutropenia (57.7%), leukopenia (24.4%) and anemia (3.8%). Rates of dose reduction due to adverse events in the palbociclib groups appeared similar among Black and Hispanic patients (37.2%) compared with the overall study populations in the PALOMA trials (39.4% to 42.2%).
“The combination of palbociclib and endocrine therapy is now a standard of care in the front-line setting for metastatic hormone receptor-positive, HER2-negative breast cancer. We have observed huge improvements in outcomes and significant disease control. In many studies, we have seen some improvements in survival for hormone receptor-positive breast cancer,” Rugo said. “However, for minority patients without data on the efficacy in the people they identify with, they may feel less confident, and providers may feel less confident understanding the toxicity and efficacy of treatment. Having data like this has significant implications in that we can now confidently treat patients and understand that we are not going to see less efficacy in minority populations.”
Future research should focus on understanding the biologic differences in cancers among various racial and ethnic groups that may help better understand how to treat patients in more focused ways, Rugo added.
“This is an important area of research that people in the research community are now paying a lot more attention to and is critical to move the field forward,” she said. “The importance of conducting trials like this is that we can do real-world analyses through large real-world databases and get a better understanding of how treatments work and how well they are tolerated to some degree. Real-world data is an important step forward in understanding how treatment affects different groups of patients.”
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Rugo HS, et al. Abstract P1-18-13. Presented at: San Antonio Breast Cancer Symposium (virtual meeting); Dec. 7-10, 2021.
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