e21202 Background: Increased systemic inflammatory state and increased inflammation within tumor micro-environment (TME) have been associated with a worse prognosis and lower responsiveness to immune checkpoint inhibitors (ICI). Systemic inflammatory immune index (SII) reflects the changes in the systemic inflammatory matrix. Studies have shown the association of SII with cancer survival and treatment outcomes. We aim to study the effect of SII on treatment outcomes in non-small cell lung cancer (NSCLC) patients being treated with ICI. Methods: We conducted a retrospective analysis on 178 NSCLC patients treated with ICIs (pembrolizumab, nivolumab, ipilimumab/nivolumab or atezolizumab) alone or in combination with chemotherapy. SII is the product of platelets multiplied by neutrophils divided by lymphocytes. Baseline and 8-week SIIs were obtained. Radiographic response, duration of radiographic response (date of best response to radiographic progression), overall survival (OS), and progression-free survival (PFS) were evaluated. A high SII was defined as a value greater than the median SII. Cox regression univariate and multivariate analyses were performed. Logistic regression, t-test, and Chi-square tests were applied. Results: Overall, 81% patients had adenocarcinoma and 19% patients had squamous, adenosquamous or large cell carcinoma. The majority of the patients were female (56.2% vs. 43.8%). Median SII at baseline was 1335. The objective response rate (ORR) was 45.1%. The disease control rate was 75.8%. The ORR was 51% in patients receiving ICI first-line compared to 35% in those who received ICI as a second-line therapy. At baseline, there was no difference in the mean SII between responders and non-responders (2146.2 vs. 1917.5, P = 0.5); however at 8 weeks, the mean SII was significantly lower in responders compared to non-responders (1198.8 vs. 2880.2, P = 0.02). A total of 15 (10.9%) patients were found to have pseudoprogression or mixed response on follow-up imaging. Among these, 11(73.3%) patients had low SII at 8 weeks (P = 0.04). The median OS was significantly higher in patients with low SII at baseline (29.6 months vs. 10.1 months, P = 0.001 95% CI 10.6 – 22.1). Similarly, there was a significant difference in median PFS in patients with low SII (14.6 months vs. 6.7 months, P = 0.002, 95% CI 5.6 – 11.6). There was no correlation between high or low SII on the incidence of immune-related adverse events. Conclusions: SII may have significant impact on OS and PFS and could be serially monitored to assess the response to ICI. A low SII may help to differentiate pseudoprogression vs. true progression. Prospective studies are needed to validate these findings. Further, it will be interesting to see if SII could be incorporated into predictive models to determine the duration of cytotoxic therapy in selected patients.
1396P Development and validation of a host-dependent, PDL1-independent, biomarker to predict 6-month progression-free survival in metastatic non-small cell lung cancer (mNSCLC) patients treated with anti-PD1 immune checkpoint inhibitors (ICI) in the CERTIM cohort: The ELY study
