Changes in lymphocyte/monocyte ratio, prognostic marker to predict overall survival in patients with advanced cancer treated with immune checkpoint inhibitor.
3047 Background: Immunosuppressive factors within the tumor microenvironment (TME) pose a barrier to response to treatment with immune checkpoint inhibitors (ICI). Monocytes alter the TME to promote cancer progression through local immune suppression and angiogenesis. Peripheral blood lymphocyte-to-monocyte ratio (LMR) may reflect the interaction between host immunity, represented by lymphocytes, and the tumor microenvironment, represented by monocytes. A low LMR in the peripheral blood may serve as a surrogate biomarker and has been associated with poor prognosis in various cancers; however, its role has not been well defined in the era of treatment with ICI. Methods: We retrospectively evaluated 1034 patients with advanced cancer treated with ICI from 2011 to 2017. We calculated LMR as ratio of absolute lymphocyte/monocyte counts at baseline and median of 21 days after first cycle of ICI (on-treatment LMR) and considered low if < 2. Overall survival (OS) was calculated from the initiation of ICI to date of death or censored at last follow-up. Median OS with 95% confidence intervals (CI) was estimated using the Kaplan-Meier method. Log rank test was used for group comparison. Results: 536 pts (52%) with LMR < 2 at baseline had shorted median OS compared to 498 (48%) with LMR≥2 (median OS 8.4 months vs 17.8 months, p < 0.001). Of 1034 pts with baseline LMR, 837 had follow up LMR evaluable. In patients with baseline and on-treatment LMR, those with baseline LMR < 2, who had on treatment LMR ≥2, had OS of 16.8 months (95% CI 10.3-23.5) compared to median OS 8.0 months (95% CI 6-9.4) for patients with on treatment LMR < 2 after first cycle of ICI, p < 0.001. Patients with baseline LMR≥2, who had on treatment LMR ≥ 2, had median OS of 23 months (95% CI 19.7-28.9), but median OS was 9.4 months (95% CI 7.1-11.1) for patients with on-treatment LMR < 2 after first cycle of ICI, p < 0.001. Conclusions: We observed a statistically significant association between not only baseline LMR but also change in LMR from baseline after first cycle of ICI and overall survival in cancer patients treated with ICI. The role of LMR at baseline and on-treatment LMR should be evaluated in further studies incorporating known additional prognostic factors for ICI therapy. [Table: see text]