RECIST 1.1 AND irRC FOR RESPONSE ASSESMENT IN PATIENTS WITH DISSEMINATED CUTANEOUS MELANOMA TREATED WITH IPILIMUMAB OR DENDRITIC CELL VACCINE

Special systems were developed for response assessment of immunooncology drugs. The role and benefits of particular system in assessing the efficacy of different immunotherapy methods are not clear yet. The objective of this study is to compare the responses on ipilimab (IPI) or dendritic cell vaccines (DCV) therapy by RECIST 1.1 and irRC criteria. Eighty two patients with unresectable disseminated or locally advanced stage III-IV melanoma were included. Fifty-five patients were treated with IPI and 27 – with DCV at the N.N. Petrov National Medical Research Center of Oncology from 2007 to 2016. Response by each system was compared to overall survival (OS). Response by both systems was a good marker for OS in IPI group (p=0,0001 for both systems) but not in DCV group (p=0,357 for RECIST and p=0,411 for irRC). Discrepancies in responses by different systems were detected in 5 patients in the IPI group and in 5 patients in the DCV group (p>0.05). The median of OS in IPI patients with PD by both systems was 8.8 mo. In case of mixed responses, (RECIST progression disease (PD) and irRC stable disease) OS in IPI group was 29.1+ mo, 16.7 mo. In the case of SD by RECIST and PD by irRC OS was 11.6+ mo. One patient with PD by RECIST and partial response by irRC lived 16.3 mo. OS in DCV group was 9.5+, 8.7, 15.3, 29.7 mo. in patients with mixed responses (PD+SD); 15,7 mo. in patient with SD by RECIST and PR by irRC. There was a trend to better overall survival of patients with PD according to the RECIST 1.1 and the absence of PD by irRC system in comparison with the PD by both systems in the treatment of IPI was revealed. In the DCV group the same pattern wasn’t found. Thus, both the RECIST 1.1 system and the irRC system are good surrogate markers for the overall survival. SD in patients receiving DCV cannot be considered a good response to therapy, since it does not improve the OS in comparison with patients who has PD by the same system. The irRC system allows to extract a subgroup of patients with better overall survival from patients with PD by RECIST among those who receive IPI but not DCV for systemic therapy of melanoma.