Background: IROC is an expanding multi-institution collaborative database which includes socioeconomic, genomic, pathologic, clinical and laboratory data in metastatic RCC patients (pts), primarily in the modern setting. Elevated baseline NLR is now an established poor prognostic factor in renal cell carcinoma (RCC) but currently has limited practical use. We hypothesized that an increase in NLR of 3 or more (NLR Failure) at 2 months on therapy could be a predictor of eventual treatment failure and shorter overall survival and thus augment the utility of this marker. Methods: Patients with complete data on NLR at time = 0 and +2 months of therapy were analyzed. Information on comorbidities, previous therapy, demographics were collected for adjusted analysis. NLR failure was defined as an increase of 3 or more compared to baseline NLR. Cox proportional hazard models were used to analyze the risk of progression and death with NLR failure at 2 months (+/- 2 weeks). Kaplan Meier graphs were constructed to trace survival functions for PFS and OS by NLR. Results: Among 165 pts; 121 were eligible (Table). NLR failure at 2 months was associated with a highly statistically significant increase in the risk of death in < 1 year (HR 6.82, 95% CI [3.16-14.70], p<0.001). In a model adjusted for NLR change, the value of baseline NLR to predict OS <1 year was non-significant (HR 1.02, p = 0.65). Similarly, NLR failure increased the risk of treatment failure in less than 6 months (HR 4.83 95% CI [2.29-10.19], p<0.001), while baseline NLR did not predict it (HR 1.03, p = 0.34). These findings were unaffected by immunotherapy vs TKI therapy. NLR failure at 2 months had a 78% (11/14) positive predictive value for survival <1 year and 86% (12/14) [p=.0001] for treatment failure in 6 months. Conclusions: In this multi-institutional cohort of RCC pts; an increase in NLR of 3 or more at 2 months following therapy start predicts for an increasing risk of death and impending treatment failure with a high PPV. The prognostic value of baseline NLR is non-significant when adjusting for NLR change. NLR failure should be validated in prospective studies and could have clinical utility in management of RCC pts.