Validation of the Princess Margaret immune oncology prognostic index (PM-IPI) for patients (pts) treated in immune oncology (IO) early phase trials.

Abstract

3070 Background: We previously developed the PM-IPI (ECOG performance status [PS] > / = 1, albumin < lower limit of normal [LLN] and > 2 metastatic sites) from a retrospective cohort of 192 pts treated in phase I IO trials (development cohort). The PM-IPI prognosticated for overall survival (OS), 90-day mortality (90DM) and was associated with improved overall response rate (ORR) and progression free survival (PFS). Our aim was to prospectively validate the PM-IPI in an independent cohort of pts treated on IO trials. Methods: We included 152 consecutively treated advanced solid tumor pts at PM from Aug 2015 to Aug 2016 in 24 IO early phase trials, targeting immune checkpoints and/or co-stimulatory molecules. Pts from the development cohort were excluded. The ability of the PM-IPI to prognosticate OS and 90DM, and predict PFS and ORR was compared with the previously published Royal Marsden Hospital prognostic score (RMI: albumin < 35g/L, LDH > upper limit of normal and > 2 metastatic sites) using the C-index (0.5 = no discrimination, 1 = perfect discrimination) and Area Under the Curve (AUC). Results: Median age was 59y (range 20-86), 28%/72% of pts were ECOG PS 0/1, and 88% had at least 1 prior systemic therapy (range 0-7). The most common tumor sites were gastrointestinal (23%), gynecological (16%), head and neck (15%) and urological (10%). Median PFS and OS were 9.0 and 39.7 wk respectively and 90DM was 14%. ORR was 7% by RECIST 1.1, immune related RECIST or immune related response criteria. In multivariable analysis, ECOG PS > / = 1 (HR 2.7, p = 0.01), albumin < LLN (HR 2.1, p = 0.01) and > 2 metastatic sites (HR 1.8, p = 0.04) were independently prognostic for OS. Pts with a PM-IPI score of 2-3 compared to 0-1 had significantly shorter OS (HR 3.3, p < 0.0001), PFS (HR 1.7, p = 0.005) and higher 90DM (OR 12.2, p = 0.019), and a trend towards lower ORR (OR 0.4, p = 0.15). The prognostic performance of PM-IPI was superior to the RMI for OS and 90DM, but not PFS and ORR (Table). Conclusions: In this independent validation cohort, the PM-IPI prognosticated for OS and 90DM and was associated with PFS. Validation in a large external cohort is ongoing. [Table: see text]