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New test detects recurring Merkel cell carcinoma sooner

A new immune system marker test may allow patients who have been successfully treated for Merkel cell carcinoma (MCC) to be stratified by risk of recurrence and potentially allow any recurrence to be detected earlier, researchers report online in the journal Cancer (Dec. 7, 2016).

The new test measures the presence of an antibody to a cancer-driving protein produced by a virus that causes MCC, according to a press release from the Fred Hutchinson Cancer Research Center in Seattle, where the research was conducted.

MCC has a high recurrence rate, with cases treated at their earliest stage returning 20% of the time, according to the press release.

“Catching and treating the recurrence before it has a chance to grow large—the difference between a cancer the size of a grape and one the size of a grapefruit—enhances the chances that immune therapy will work,” said the paper’s lead author, Dr. Paul Nghiem, a member of Fred Hutchinson Cancer Research Center, the head of the Division of Dermatology at the University of Washington medical school and a clinician at the Seattle Cancer Care Alliance, said in the release.

According to the paper, most MCC in the U.S. is caused by the Merkel cell polyomavirus (MCPyV), and prior research has shown that antibodies to MCPyV oncoprotein (T-antigens) have been correlated with MCC tumour burden.

To see if titres of the antibodies could be used to evaluate prognosis and assist in disease surveillance, the investigators prospectively followed a cohort of 219 patients whose initial MCC had been successfully treated with surgery or radiation (median follow-up, 1.9 years). Among the seropositive patients, antibody titre and disease status were serially tracked.

The efficacy of the antibody test at detecting recurrence was compared to radiologic imaging, which is the method most commonly employed.

Over a five-year period, the antibody test was better at picking up small traces of MCC when it first returned, often suggesting the cancer was recurring well before tumours were visible by imaging. As well, the blood test is less expensive than traditional imaging and spares the patient exposure to radiation and contrast dye.

Because of the rareness of MCC and the fact that not all MCC patients produce these antibodies, it is not suitable for initial diagnosis, said Dr. Nghiem. Instead, all MCC patients at his clinic now receive the test at the time of diagnosis.

“The findings highlight how monitoring the robustness of the immune system provides key insights into cancer treatment, and they are emblematic of a broader shift in how physicians can track disease,” said Dr. Nghiem. “It underscores a key tenet of immune therapy—that your immune system is naturally attuned to fighting cancer and the challenge is how best to harness that.”

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