Study Backs CP-GEP Tests’ Accuracy

Patients with clinically node-negative primary cutaneous melanoma undergoing sentinel lymph node biopsies (SLNBs) who were classified as “high risk” according to CP-GEP tests were approximately three times more likely to be SLN positive, according to data presented October 13 at the Society of Melanoma Research’s annual meeting and summarized the following week at the American Society for Dermatologic Surgery (ASDS) conference.

Vernon Sondak, MD, presented data from the MERLIN_001 study, which he said was the largest prospective trial of a genomic assay conducted in melanoma. “Age is just a number,” Dr. Sondak said of deciding when to conduct SLNBs. He said dermatologists must keep in mind “how important personalizing the data is,” which is why CP-GEP and i31-GEP tests are so useful.

The MERLIN_001 study included adult patients with primary tumor thickness of at least 0.8 mm but no more than 4.0 mm (T1b – T3b) on initial tumor biopsy with clinically negative regional lymph nodes, or primary tumor thickness of less than 0.8 mm but at least one “high risk” feature. Eligible patients had no prior surgery or prior invasive melanoma in any nodal basin potentially draining the primary site, and no prior or concurrent primary invasive melanoma of T 1b or greater at any site within 5 years. Biopsies were within 120 days of study enrollment. Mucosal, vulvar, perianal, and ocular primary tumors and atypical Spitz tumors were excluded.

Between September 2021 and June 2024, a total of 2,141 patients were screened; 1,846 patients from nine study sites underwent SLNB, with an assay success rate of 97.7%. Successful CP-GEP testing was performed on 1,686 patients. The study sites and the central GEP laboratory were blinded.

Overall, 1,062 patients were classified as high risk by CP-GEP, and 624 were classified as low risk. Among the high-risk patients, 23.8% had positive SLN rates; among those classified as low-risk, 7.1% were positive.

The key to the study, Dr. Sondak said, was the care with which it was performed.

“We felt very strongly that if we were going to change that standard of care … that it had to be done in a very thoroughly conducted, prospective clinical trial, where everyone was blind to the result,” he said.