Racial/Ethnic Disparities in Genomic Sequencing
As scientists learn more about which genetic mutations are driving different types of cancer, they're targeting treatments to small numbers of patients, with the potential for big payoffs in improved outcomes. But even as we learn more about these driver mutations, a new study published by Spratt et al in JAMA Oncology suggests the science might be leaving racial and ethnic minorities behind.
“Even when studies have a reasonable ‘relative’ representation of racial and ethnic minorities, the overall ‘absolute’ number of minorities examined may not be enough to detect small differences in the cancer's genome,” said Daniel Spratt, MD, Assistant Professor of Radiation Oncology at the University of Michigan Medical School.
Studies such as The Cancer Genome Atlas (TCGA), a federally funded project to understand the molecular characterization of various cancer types, are discovering uncommon genetic mutations in small percentages of patients. This knowledge has led to new cancer treatments targeting these mutations, which have improved outcomes among patients with targetable mutations.
“If you're using these data to identify new mutations and develop new drugs targeting those mutations, then we need to know what mutations are present in patients of different races. Otherwise, we may be unintentionally widening disparities,” Dr. Spratt explained.
Study Findings
Dr. Spratt and colleagues looked at tumor samples studied as part of the TCGA. The samples, from 10 different cancer types, were somewhat racially diverse. About 12% were African American, which is representative of the U.S. population. Only 3% were Asian, slightly lower than the true 5% of the overall population, and only 3% were Hispanic, much less than the accurate 16% of the overall population.
But when researchers logged the actual number of tumor samples from minorities, of 5,729 samples, 660 were African American, 173 were Asian, and 149 were Hispanic—compared with 4,389 from white patients.
Researchers analyzed these numbers and determined that there were not enough samples from any minority group to identify a mutation that would occur in 5% of those patients. On the other hand, there were enough samples in nearly every tumor type to detect a mutation occurring in 5% of white patients.
In many cases, a mutation associated with a particular cancer impacts only a small percentage of patients. For example, only 3% of lung cancer patients have alterations in ALK, yet multiple U.S. Food and Drug Administration–approved drugs exist to improve survival in these particular patients.
“In current practice, we do have drugs aimed at very infrequent alterations,” Dr. Spratt said. “If we can't detect a mutation present at a lower frequency, we wouldn't be able to develop a treatment against it.”
Many studies have demonstrated how cancer behaves differently in different racial and ethnic groups. It's also known that certain cancer types are more common or more aggressive among certain races—for example, about 50% of Asians with lung cancer have a mutation in EGFR.
The study authors suggest more collaborative efforts—including between industry, government, and academia—are necessary to collect larger numbers of tumor samples from diverse racial and ethnic groups. As precision medicine becomes increasingly important in cancer treatment, identifying mutations will allow researchers to target and adjust clinical trials.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
