In previous reports it has been demonstrated that the 18F-FDG PET/CT performs better than contrast-enhanced CT in assessing the response to immunotherapy treatment in patients affected by metastatic melanomas. Aim of the present study was to evaluate if the first 18F-FDG PET/CT scan performed after the completion of 4 cycles of Ipilimumab treatment was predictive of patient clinical outcome.
26 patients who performed a PET/CT scan before treatment (PET0), after 4 cycles of Ipilimumab (PET1) and at least an additional later evaluation without starting new therapeutic regimen (PET2), were retrospectively evaluated. Response to treatment was evaluated according to PERCIST criteria for PET1 and PET2 and compared with patient clinical outcome. A total of 69 metastatic lesions were also singularly analyzed.
PET1 were performed after a mean of 6 weeks from the end of IPI and PET2 after a mean of 12 weeks from PET1. Patients were classified at PET1 as having progressive metabolic disease (PMD) in 15 cases, stable metabolic disease (SMD) in 6, partial metabolic response (PMR) in 2 and complete metabolic response (CMR) in 3. Discordant results between PET2 and PET1 were observed in 6 patients (from SMD to PMD in 4 cases, from SMD to CMR in 1 and from PMD to CMR in 1).
The results showed that the first PET/CT evaluation after IPI was not always representative for the definitive response to treatment. The immediate start of a new therapeutic line can be proposed for PMD, in all other cases and in particular for SMD an early PET/CT restaging should be performed to confirm the patient clinical outcome.
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All authors have declared no conflicts of interest.