Tumor size a determining factor in melanoma drug’s efficacy

Researchers at Mayo Clinic have found that pretreatment tumor size is the primary reason some patients with advanced melanoma respond better than others to the experimental immunotherapy MK-3475 (Merck).

Their findings were presented last week at the 50th annual meeting of the American Society of Clinical Oncology. The researchers, from Mayo Clinic in Florida, say their findings could lead to different treatment strategies and perhaps influence staging of advanced melanoma.

“We demonstrate baseline tumor size is the most important clinical factor for patients with metastatic melanoma receiving MK-3475,” Mayo Clinic oncologist and lead investigator Richard W. Joseph, M.D., tells Dermatology Times. “This is significant because clinicians have long felt that baseline tumor size was important but there was a lack of data to support this opinion. Now that we have demonstrated the importance of baseline tumor size, this variable should be considered and documented in all clinical studies to allow us to better understand the patient population.”

According to Dr. Joseph, the study is the first “robust assessment” of the impact of baseline tumor size on clinical endpoints in metastatic melanoma patients being treated with MK-3475. He adds that the traditional staging system does not account for the total volume of disease or baseline tumor burden. Dr. Joseph notes that this doesn’t mean the drug doesn’t work in patients with a large amount of disease, just that its efficacy is significantly less than in those with small-volume disease.

A Mayo Clinic news release notes that the study’s findings suggest that decreasing the baseline tumor size through surgery or other means, then treating with MK-3475, may be a more effective treatment strategy. The authors note that follow-up studies will be necessary to explore this further.

Dr. Joseph and colleagues have enrolled 20 additional patients since the trial was re-opened in April through an expanded access program. Merck funded the study.

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