September 19, 2016
2 min read

Colorectal cancer genes unique to black patients linked to worse outcomes

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Researchers who previously identified a panel of genetic mutations that are unique to black patients with colorectal cancer have now found these mutations are associated with more aggressive tumors and increased risk for recurrence and metastasis, according to data published in the Journal of the National Cancer Institute.

“This study is significant because it helps shed further light on why colorectal cancers are more aggressive in African Americans compared to other groups,” Joseph E. Willis, MD, chief of pathology at University Hospitals Case Medical Center, and professor of pathology at Case Western Reserve School of Medicine, said in a press release. “While mortality rates for Caucasian men with colorectal cancer have decreased by up to 30%, they have increased by 28% for African American men since 1960.”

Joseph E. Willis

Sanford D. Markowitz

Previously, as part of the federal GI SPORE program, Willis and colleagues used whole-exome and targeted DNA sequencing to compare somatic mutations in 103 colorectal cancer samples from black patients with 129 samples from white patients. Ultimately, they identified 15 genes that had a 3.3-fold increase in mutations among the black patients’ samples, with 41% of samples having somatic mutations in at least one of these genes.

“We wondered if colon cancer is the same disease molecularly in African American individuals as it is in Caucasian individuals. Or could colon cancer be the same disease behaving differently in one population compared to another,” Sanford D. Markowitz, MD, PhD, Ingalls professor of cancer genetics at Case Western Reserve School of Medicine and medical oncologist at University Hospitals Case Medical Center, said in a press release. “This study gave us our answer. Colon cancer in African American patients is a different disease molecularly.”

Building on this research, the team evaluated outcomes associated with the previously identified genetic mutations in 66 black patients with stage I-III colorectal cancer (median follow-up, 57 months).

Among 27 patients whose cancers harbored these gene mutations, eight developed metastatic disease, compared with four of the 39 cancers that did not have these mutations (P = .03).

Furthermore, stage III cancers with the gene mutations were almost three times more likely to relapse, with seven out of 15 mutation-positive cases relapsing compared with three out of 18 mutation-negative cases relapsing (P = .03).

“Our study suggests that [African American]-CRC gene mutations may define a high-risk subset of colon cancers that contributes to the overall observed disparity in colon cancer outcomes seen in African Americans,” the researchers wrote. – by Adam Leitenberger

Disclosures: The researchers report no relevant financial disclosures.