SOURCE: American Society of Clinical Oncology, news release, May 29, 2015
FRIDAY, May 29, 2015 (HealthDay News) -- The first genetic "marker" -- or signal -- to predict response to the cancer drug Keytruda (pembrolizumab) has been identified by researchers.
The marker -- mismatch repair (MMR) deficiency -- predicted responses to the drug in patients with several different types of cancer, the study authors said.
Among patients with colon cancer, 62 percent of those with MMR-deficient tumors showed tumor shrinkage when taking Keytruda, compared with no tumor shrinkage in patients without this genetic signal.
The response rate among patients with other MMR-deficient cancers was 60 percent, according to the study.
"This study is really about bridging immunotherapy and genomics for the benefit of patients, and it has implications for a broad range of cancers," study lead author Dr. Dung Le said in a news release from the American Society of Clinical Oncology (ASCO).
Le is an assistant professor of oncology at Johns Hopkins Kimmel Cancer Center in Baltimore.
Findings from the study were scheduled to be presented Friday at the ASCO annual meeting in Chicago. Findings presented at meetings are generally considered preliminary until published in a peer-reviewed journal.
MMR-deficiency occurs in a number of types of cancers, including colon (colorectal), stomach, small bowel, prostate, ovarian and endometrial (uterine), according to the researchers.
Testing for MMR-deficiency is widely available and may help doctors identify a larger number of cancer patients who might benefit from Keytruda and similar drugs, the researchers said.
"Opening the door to this effective new therapy would be a breakthrough for this subset of patients with metastatic [spreading] colon cancer and other hard-to-treat cancers," Le added.
The American Academy of Family Physicians has more about cancer treatment.