LAUSR

e20026 Background: PD1/PDL1 treatments have become the main therapy in advanced stages of NSCLC due to its significant increase in overall survival (OS), but recently, combination with chemotherapy in locally advanced stages is showing promising results. Many studies have described the neutrophil-to-lymphocyte ratio (NLR) and platelets-to-lymphocyte ratio (PLR) as indicator of systemic inflammation, that could be use as biomarker of response to immunotherapy. In our study, we described the effect of neoadjuvant chemo-immunotherapy in Complete Blood Count (CBC) parameters and evaluated their relationship with pathological responses. Methods: Immune cell populations of 46 resectable stage IIIA NSCLC patients treated with neo-adjuvant chemo-immunotherapy from NADIM clinical trial were analysed. Samples were extracted before initiating the neo-adjuvant treatment with nivolumab plus carboplatin and at the third cycle before patients underwent surgery. We classified patients in 3 subgroups of pathological response assessed in the resection specimen: complete response (pCR), mayor response (< 10% viable tumour) and incomplete response (> 10% viable tumour). Wilcoxon and Mann-Whitney U statistic test were used to evaluated differences between pre and post treatment and between pathological responses groups respectively. Results: From 46 patients, 5 patients did not undergo surgery, so they were excluded from the analysis. Absolute numbers (x103cells/µl) of CBC were significantly reduced after neo-adjuvant treatment in patients, leucocytes (8.80 vs 6.64), Eosinophil (0.22 vs 0.15), Monocytes (0.72 vs 0.62), Neutrophils (5.53 vs 3.53), Haemoglobin (35.82 vs 29.68), Platelets (292.44 vs 227.22), NLR (2.73 vs 1.71) and PLR (143.34 vs 115.85) except Lymphocytes (2.22 vs 2.25) and Basophils (0.06 vs 0.05). Moreover, when the analysis was done by subgroups of pathological responses, PLR variation was significantly different between pCR and incomplete response (-21.33 vs -76.98) whereas NLR and the rest of the immune populations were no different between subgroups. Conclusions: In our study, NLR is not associated to chemo-immune neo-adjuvant treatment response. Nevertheless, in our cohort a higher decrease on PLR post neo-adjuvant treatment is associated to an incomplete pathological response.