Researchers demonstrated the combined positron emission tomography / computed tomography ( PET / CT ) scanning early in treatment could identify whether the therapy will benefit a particular patient. As the therapy has potentially serious side effects, early determination of ineffectiveness could avert unnecessary risk exposure and provide the option of a different treatment.

Advanced melanoma, a type of skin cancer that has spread to other areas of the body, has a poor prognosis, but immune checkpoint inhibitor therapy can be effective for some patients. The study was published in The Journal of Nuclear Medicine 

Immune checkpoint inhibitors (ICI) block certain proteins made by immune system cells, such as T cells, and some cancer cells that were keeping the immune system T cells from killing the cancer cells. When these checkpoint proteins are blocked by inhibitors, the immune system can function again and T cells are better able to destroy cancer cells.

Determining response to ICI therapy has been challenging. "Current anatomic CT-based response criteria are typically performed at the earliest two to four months into treatment and are limited in their ability to assess stable disease and pseudoprogression," explained Steve Y. Cho.

The study evaluated the use of 18 F-fluorodeoxyglucose- (FDG) -PET / CT scanning as an early predictor of response to ICI therapy in 20 patients with advanced melanoma. The patients each had three scans: prior to treatment, at 21 to 28 days and at four months. The researchers developed criteria to predict eventual response to ICI with 100% sensitivity, 93% specificity and 95% accuracy. 

Cho notes, "When  18 F-FDG PET-based response criteria were combined with CT-based criteria, we were able to more accurately differentiate eventual clinical benefit." Based on our data, we have proposed a combined PET and CT-based response to immune-checkpoint inhibitor therapy in advanced metastatic melanoma. Interestingly, we found a small Increase in  18 F-FDG tumor uptake at this early time point That May implicate an active immune mediated 'flare' as a good indication That the tumor is responsive to the immune therapy. "

He cautions, "While immune therapies, including the particular class of immune checkpoint inhibitors used in this study, promise new hope for durable tumor responses and remission for a variety of cancers, they are not without cost. causing immune-related adverse events, which can limit the risk of side effects and allow for initiation of other therapies. "The next step is for further studies with larger cohorts.

The National Institutes of Health states that more than 1 million people in the US are living with melanoma and estimates that in 2017 more than 87,000 new cases of melanoma will be diagnosed, and the cancer will cause nearly 10,000 deaths. According to the American Cancer Society, the five-year survival rate for individuals with stage 4 melanoma is only about 15 to 20 percent.

Looking ahead, Cho points out, "Incorporation of more effective and early PET- and CT -based response assessment criteria could also be used to more optimally assess newborn immune-based therapies in drug development for melanoma and other tumors ."