Prognostic value of post-treatment ¹⁸F-FDG PET/CT studies in melanoma patients receiving ipilimumab

Objectives: Ipilimumab (ipi) is a newly approved immunotherapeutic drug. Aim of our study is to evaluate the predictive role of post-treatment ¹⁸F-FDG PET/CT as regards clinical outcome in melanoma patients receiving ipi.

Methods: This is a prospective study, which enrolled 40 patients with metastatic melanoma. PET/CT with FDG was performed prior and after 4 cycles of ipi. We evaluated the PET/CT scans qualitatively and quantitatively. The number of newly developed lesions, their locations as well as both the changes in SUVmax and SUVmean were compared. FDG findings were correlated to CT in order to exclude false positive results. Patients with only brain metastases were excluded.

Results: Best clinical response showed that 21 patients had stable disease (SD), 8 patients had progressive disease (PD), 9 patients had partial remission (PR) and 2 patients had complete remission (CR). Patients with CR and PR had no new lesions in the late scan, while patients with PD had more than 10 newly developed lesions. Patients with SD demonstrated up to 10 newly developed lesions. A multivariate analysis also including the changes in the LDH level in the different response groups is going to be performed statistically.

Conclusion: Preliminary results show that the change in the absolute number of new lesions in metastatic melanomas receiving immunotherapy is a better predictor of clinical response than the changes in the SUV values of the single lesions. In particular, the absence of new lesions correlated to PR or CR, more than 10 new lesions with PD, and between 0 and 10 new lesions with SD. Research Support: N/A $$graphic_9310923F-197E-435B-93A9-767F3431AD7F$$