Keytruda (Pembrolizumab) Shows Promise for Advanced Merkel Cell Carcinoma

Results of a small clinical trial show that more than half the patients with Merkel cell carcinoma, a rare but aggressive type of skin cancer, improved when they took the immunotherapy drug Keytruda (pembrolizumab). And the improvement appears to be lasting longer than would be expected with standard treatment. This is a significant finding because there are currently no drugs that have been approved by the US Food and Drug Administration (FDA) to treat Merkel cell carcinoma. Researchers studying Keytruda and other drugs are trying to provide more treatment options for people with this type of skin cancer.

While skin cancer is by far the most common type of cancer in the United States, Merkel cell carcinoma is not common. It’s thought that about 1,500 cases of Merkel cell carcinoma are diagnosed in the United States each year. It tends to spread quickly and can be hard to treat. While it often responds to chemotherapy, the improvement usually lasts only about 3 months.

Researchers from cancer research centers across the US studied 25 people who took part in the clinical trial. All had Merkel cell carcinoma that had spread, and none had received chemotherapy. They were all given Keytruda. Fourteen of them (56%) improved, including 4 who had a complete response, meaning all signs of their cancer disappeared. After 6 months, 12 of the 14 were still doing well.

The study was presented April 19 at the annual meeting of the American Association for Cancer Research in New Orleans, and published online in The New England Journal of Medicine.

Keytruda is already approved to treat some advanced cases of melanoma skin cancer and lung cancer. It works by targeting PD-1, a protein on some immune cells in the body that stops them from attacking cancer cells. Drugs that block the protein can help the immune system recognize the cancer cells and attack them.

The most common side effects of this drug are fatigue, cough, nausea, itchy skin, rash, decreased appetite, constipation, joint pain, and diarrhea. Less common but more serious side effects can include inflammation of the lung, colon, hormone-producing glands, liver, heart, and other organs.

Preventing skin cancer and finding it early

Risk factors for Merkel cell carcinoma include infection with a virus called Merkel cell polyomavirus (MCV) and exposure to ultraviolet (UV) rays from the sun, tanning beds, and other sources.

Help lower your risk for Merkel cell carcinoma and all types of skin cancer by protecting your skin from UV rays:

  • When you are out in the sun, wear clothing and a wide-brimmed hat to protect as much skin as possible. Protect your eyes with sunglasses that block at least 99% of UV light.
  • Use a broad spectrum sunscreen with SPF of at least 30. Put more on at least every 2 hours, as well as after swimming or sweating.
  • Limit your direct exposure to the sun, especially between the hours of 10 a.m. and 4 p.m., when UV rays are strongest.
  • Avoid tanning beds and sunlamps, which can cause serious long-term skin damage and contribute to skin cancer.

Many doctors also recommend performing a self-exam of your skin about once a month, and having your skin examined by a health care professional during routine medical check-ups. Report any skin changes you’re concerned about, including:

  • Any new spots
  • Any spot that doesn’t look like others on your body
  • Any sore that doesn’t heal
  • Redness or new swelling beyond the border of the mole
  • Itching, pain, or tenderness
  • Oozing, scaliness, or bleeding

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

PD-1 Blockade with Pembrolizumab in Advanced Merkel-Cell Carcinoma. Published online April 19, 2016 in The New England Journal of Medicine. First author Paul T. Nghiem, MD, PhD, University of Washington Medical Center, Fred Hutchinson Cancer Research Center, Seattle.

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