DENVER – A newly-available test based on the results of a simple blood draw has proved useful for detecting early recurrences of Merkel cell carcinomas in those patients who produce antibodies to the Merkel polyomavirus oncoprotein at initial diagnosis.
Known as AMERK, the test can be used at diagnosis to determine which patients have the oncoprotein antibodies and performed at routine followups as an indicator of recurrence in asymptomatic, antibody-positive patients.
The test already has been shown to alert clinicians to the presence of surgically manageable metastases that would have otherwise gone undetected until symptoms prompted a tomographic scan, Dr. Astrid Blom reported at the annual meeting of the American Academy of Dermatology. She presented two cases of surgically operable metastatic Merkel cell tumors, one metastatic to the kidney and the other to the pancreas; both were detected via increasing titers of oncoprotein antibodies in otherwise asymptomatic patients.
Nearly 40% of Merkel cell carcinomas recur. Performing a predictive blood test at routine followups can be a reassuring measure in those patients with negative findings. It also can be an early indicator of metastasis in otherwise asymptomatic patients who made oncoprotein antibodies at diagnosis and were successfully treated for Merkel call carcinoma, she said.
Merkel cell polyomavirus drives about 80% of the approximately 2,000 Merkel cell carcinomas that are diagnosed each year. About half of affected patients produce oncoprotein antibodies to the polyomavirus, which are detectable at diagnosis. The AMERK test is useful only for followup of those patients with oncoprotein antibodies. Patients who lack initially detectable levels of oncoprotein antibodies at diagnosis do not later produce antibodies should their disease recur, reported Dr. Blom of the University of Washington, Seattle, where the test was developed and is performed.
The clinical utility of AMERK, a 75-step assay that takes nearly 2 days to perform, was verified using 1,342 samples from 104 controls and 519 patients from around the world, with data correlating to 3,018 status updates. The data analysis was limited to the 217 patients with adequate follow-up data.
A simple blood draw was collected and sent for analysis at the University of Washington, Seattle. Oncoprotein antibodies were detected in 52% of 217 patients with incident cases of Merkel cell carcinoma and in 2% of 530 control subjects. The antibody titers in controls were barely detectable, however, unlike the levels seen in the patients. The sensitivity of the test was 82%, and the specificity was 98%; the negative predictive value was 99%, and the positive predictive value was 78%.
Levels decrease by 90% or more over the course of the year after successful surgical treatment of Merkel cell carcinomas. When the cancers recur, at least a 10-fold increase in oncoprotein antibody titers are noted.
Support for the development of the AMERK test came from the National Institutes of Health, the National Cancer Institute, and the American Cancer Society and from private donors and patients.
RESOURCES:
Information about the test is available online at http://www.merkelcell.org/sero/
A video that discusses the antibody test can be viewed here.
Dr. Kelly Paulsen, et.al. published the scientific paper that first described the test (Cancer Res. 70(21): 8388-97).
How to order the Merkel virus serology test
Physicians and staff based outside of the University of Washington system should contact their local laboratory where the patient will have their blood sample collected to initiate the process.
The local laboratory "send out test coordinator" should contact the UW Reference Laboratory Services Call Center at 206-685-6066. UW Reference Laboratory Services will set up an account for the ordering physician or clinic; collect the required billing and reporting information; and provide requirements for sample collection, processing and shipping from the local laboratory. Once this one-time administrative process is complete, patient samples can be collected routinely from that facility for the Merkel antibody test (name of test is "AMERK").
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