FDG PET/CT effectively monitors immunotherapy for melanoma patients

Measuring the effectiveness of treatment in metastatic melanoma patients is difficult, but a study published in the March issue of the Journal of Nuclear Medicine found 18F-FDG PET/CT could accurately monitor immunotherapy with ipilimumab in these patients.

“Checkpoint inhibitor therapy is now a standard therapy for metastatic melanoma,” said Wolfgang A. Weber, MD, of Technical University Munich, Germany, in a prepared statement. “However, there were concerns about whether FDG PET/CT could be used to monitor tumor response to this immunotherapy, because inflammatory reactions to the immunotherapy may cause false positive findings. The present study shows that tumor response to checkpoint inhibitor therapy with ipilimumab can be assessed accurately by FDG PET after completion of ipilimumab therapy.”

Weber and colleagues assessed 60 patients with metastatic melanoma who received FDG PET/CT scans pre- and post-treatment. The team created a new response criteria based on the change in the sum of standard uptake value normalized to lean body mass (SULpeak) of up to five lesions. The team found Positron Emission Tomography Response Criteria in Solid Tumors (PERCIST) was significantly correlated with survival of those with advanced melanoma.

Additionally, a slight modification of PERCIST using a 5-lesion analysis—imPERCIST5—improved the prognostic value of response when using 18F-FDG PET/CT.

The findings may important implications for personalizing patients’ therapy plans.

“FDG PET/CT is routinely used to stage melanoma. The present study suggests that it also can be used to monitor tumor response to ipilimumab therapy and predict outcome,” Weber said in the same statement. “FDG PET can identify patients with favorable and unfavorable prognoses—leading to therapy escalation (e.g., combination immunotherapy) or de-escalation (e.g., reduced number of therapy cycles).”