Clinical and biochemical parameters as predictors of response to checkpoint inhibitors (CPI): A single institution experience.

Abstract

e14590 Background: The benefit of CPI is limited to a subgroup of patients. Significant toxicity and financial burden make it imperative to identify biomarkers predictive of clinical benefit. We aimed to analyze if immune related adverse events (irAE), laboratory parameters (besides PD-L1 status), prior chemotherapy and concomitant medication use could predict response to CPI. Methods: 216 consecutive patients treated at RPCI with single/multiple CPI from 2011 to 2016 were identified. Demographics, irAE (CTCAE v4.03), concomitant medication use, response (RECIST v1.1) and laboratory parameters were recorded. Progression free (PFS) and overall survival (OS) were calculated. Clinical benefit (responder) was defined as objective response or stable disease with PFS ≥ 6 months. Statistical analysis was performed using SAS v9.4. Results: 185/216 patients (86%) had clinical outcomes with first CPI available (55.7% melanoma, 28.1% lung, 10.8% kidney, 3.8% bladder, 1.6% others), 14% died before disease assessment. Median age was 61 years; 64% were males. 31% were responders (R); 69% non-responders (NR). Median PFS and OS for R were not reached and for NR were 4.7/7 months (p < 0.001). 26% R developed rash vs. 12% NR (p = 0.02). irAE diarrhea was associated with better OS (p = 0.03); rash with better PFS (p = 0.007) and OS (p = 0.05). Concomitant beta-blocker/NSAID use was noted in 35%/28% R vs 20%/12% NR (p = 0.04; p = 0.01). Higher median absolute eosinophil (AEC) and absolute lymphocyte count (ALC) were noted in R (400 and 2000/µl in R vs. 300 and 1600/µl in NR; p = 0.008 and 0.024). NR were noted to have a higher median lactate dehydrogenase (LDH) of 565 vs. 503 (p < 0.001). AEC > 100/µl and ALC > 1000/ µl were associated with better OS (P = 0.03; P = 0.001). Absolute neutrophil count (ANC) > 7500/µl and leucocyte count > 8750/ µl were associated with inferior PFS (p = 0.005; P = 0.02) and OS (p = 0.002; p = 0.03). Pre-CPI chemotherapy did not correlate with response to CPI. Conclusions: Among irAE, diarrhea and rash predicted improved outcomes. Eosinophilia, lymphocytosis, neutrophilia, leukocytosis and LDH could serve as potential prognostic biomarkers to CPI. Prospective studies are warranted to validate these findings.