STATISTICS CONTINUE TO SHOW large gaps in cancer mortality between Black Americans and white Americans for most cancer types. In fact, Black men with colorectal cancer currently die at rates 44% higher than white men with the same cancer, while Black women die at rates 31% higher compared to white women.
Observing poorer outcomes among Blacks in their own patients with colorectal cancer, researchers at Memorial Sloan Kettering Cancer Center (MSK) in New York City sought to drill into biological differences that could be contributing factors to this disparity. Henry Walch, a computational biologist at the Marie-Josée and Henry R. Kravis Center for Molecular Oncology at MSK, presented their findings April 17 at the American Association for Cancer Research (AACR) Annual Meeting 2023 in Orlando, Florida. (The AACR publishes Cancer Today.)
Analyzing data from 4,441 colorectal cancer survivors of different ancestries who received genetic testing at MSK, including 245 people of African ancestry, the study found that the African ancestry group had a median overall survival of 45.7 months from time of diagnosis, compared with 67.1 months for the European ancestry group.
The study also looked at DNA sequencing data from the patients and found that patients of African ancestry had fewer actionable mutations, suggesting a lack of therapeutic options compared with other groups. For example, patients of African ancestry were less likely to have tumors that tested positive for BRAF-related mutations, genetic alterations that are often associated with a poor prognosis but for which targeted treatments are available. The study also showed that 13.5% of patients of African ancestry qualified for immunotherapy based on Food and Drug Administration guidelines for certain biomarkers, including microsatellite instability and tumor mutational burden. In contrast, 20.4% of patients of European ancestry qualified.
“I think if anything it highlights the urgent need to find new treatment strategies,” Walch said at a press conference. “It highlights the need to find new targets for these patients because they don’t have the molecular profiles that would qualify them for more powerful treatments that they might receive otherwise.”
Researchers found that mutations in the adenomatous polyposis coli (APC) gene, a tumor suppressor that is shown to be involved in the development of many colorectal cancers, suggest different implications for people of African ancestry. While somatic alterations in this gene are often associated with longer survival for patients at MSK, these mutations did not appear to have any prognostic value for patients of African ancestry. The findings add to a growing body of research that will only get richer as study populations reflect the diversity of the population, Walch said.
“This study is part of a larger effort where we aim to understand the reasons behind poor outcomes in African American patients with colorectal cancer. Our ultimate goal is to identify opportunities to intervene and improve outcomes in this underserved population,” Walch said. Researchers from MSK plan to broaden the study to incorporate patients’ environmental exposures, lifestyle and socioeconomic factors.
Lisa Newman, a breast surgeon and researcher at Weill Cornell Medicine and NewYork-Presbyterian who studies genetic differences among Black women with breast cancer, moderated the discussion at the press conference. “As we uncover more broadly the comprehensive genetic profiles of tumors representing diverse patients, we are going to develop novel actionable patterns that will have clinical significance,” she said. “If we continue to study cancer in very homogeneous, uniform populations, we’re going to miss a lot of information in improving outcomes.”
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