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Last May, Keytruda (pembrolizumab) became the first ever drug approved by the U.S. Food and Drug Administration to fight cancers based on specific tumor genetics, rather than where in the body the tumor occurs.
The drug also gained attention after former President Jimmy Carter announced in 2015 that Keytruda had beaten back his brain cancer.
But would it work against advanced melanomas, the deadliest of skin cancers?
"Melanoma has always been considered an 'outlier' cancer in that it does not respond well to classical chemotherapy used for other cancers," noted one specialist, dermatologist Dr. Doris Day, of Lenox Hill Hospital in New York City. She was not involved in the new study.
The new study was funded by Keytruda's maker, Merck, and included more than 1,000 patients with stage 3 melanoma.
All had undergone a complete surgical removal of their tumors, but they were at high risk of a cancer recurrence.
Patients were randomly assigned to take either a 200-milligram dose of Keytruda every three weeks for a year (total of 18 doses), or a placebo.
After a median follow-up of 15 months, 135 of the 514 patients in the Keytruda group had been diagnosed with recurrent melanoma or had died, compared to 216 of the 505 patients in the placebo group.
The 12-month survival rate without any sign of cancer's return was about 75 percent for patients in the Keytruda group and 61 percent for those in the placebo group.
That meant that statistically speaking, those in the Keytruda group were 43 percent less likely to have recurrent melanoma, the researchers said.
The findings were presented Sunday at the annual meeting of the American Association for Cancer Research (AACR) and they were simultaneously published in the New England Journal of Medicine.
"Patients with stage 3 melanoma have metastatic disease in one or more regional lymph nodes," said researcher Dr. Alexander Eggermont, director general of Gustave Roussy Cancer Campus Grand Paris in Villejuif, France.
"A patient's risk of recurrence depends on the number of lymph nodes affected and the tumor load," he explained in an AACR news release. "Those classified as having a high risk of recurrence have one or more regional lymph nodes with melanoma metastasis [spread]."
Keytruda belongs to a class of drugs called PD1 inhibitors, which work by targeting a cellular pathway that helps the body's own immune system attack the cancer cells. The drug targets tumors with DNA known as microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR). These gene abnormalities affect repair mechanisms inside the cell.
One expert in caring for melanoma patients said Keytruda could be a breakthrough treatment.
"PD1 inhibitors are part of a class of medications called checkpoint inhibitors, and I cannot overstate the value of these new agents for the treatment of metastatic melanoma," said Dr. Craig Devoe. He's acting chief of hematology and medical oncology at Northwell Health Cancer Institute in Lake Success, N.Y.
"This study further supports the use of this class of medications in the preventative setting," said Devoe, who wasn't connected to the study. He also noted that there are relatively few side effects with these medications. But there is one drawback.
"A major concern is the very high cost of these agents to patients and society," Devoe said, with a typical course of treatment costing more than $150,000.
Currently, the PD1 drugs Yervoy (ipilimumab) and Opdivo (nivolumab) are approved in the United States for treatment of patients with high-risk stage 3 melanoma that has been completely removed by surgery.
"We hope that these data will lead to regulators in the United States and Europe approving pembrolizumab as a new treatment option for these patients," Eggermont said.
For her part, Day said the new findings are encouraging, but "the test will be maintaining results and learning how to combine the drugs in order to minimize resistance and increase cure rates."
-- Robert Preidt
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