966P Evaluation of the Prognostic Marker of PD-L1 Expression after Combined Radio-Chemotherapy in Patients with Non-Small Cell Lung Cancer (NSCLC) Stage III

The PACIFIC study showed that pts with locally advanced, unresectable NSCLC after radio-chemotherapy derived a benefit in PFS and OS when treated with durvalumab. In a post hoc analysis this effect was limited to pts with a PD-L1 of >1%. In contrast, in pts with PD-L1 of <1%, no benefit was seen partly due to the fact that the outcome in the control arm was surprisingly favorable. Thus, it could be speculated that lack of PD-L1 expression confers a favorable outcome after radio-chemotherapy in stage III NSCLC. To address the question, whether the prolonged OS in the control group with lack of PD-L1 expression was reproducible we analyzed the PFS and OS in a group of 99 pts with stage III NSCLC homogeneously treated with radio-chemotherapy similar as in the PACIFIC trial and not progressing after radio-chemotherapy. Clinical data, tumor characteristics and outcome were systematically captured from the data base of the certified lung cancer center Oldenburg, including the PD-L1-score. In cases, where the PD-L1 expression had not been evaluated, the available tissues samples were reanalyzed for PD-L1 expression by Hematopathology Hamburg, after informed consent of the surviving pts had been obtained. For statistical analyses, log rank test as well as multivariate analyses were performed. The study showed that the expression of PD-L1 is independent from gender and histology. The median OS of the pts with an expression of PD-L1 <1% was 20 months (KI 10.5 – 29.5) and with an expression ≥1% 28 months (KI 16.5 – 39.3), however this difference was not statistically significant with a p-value of 0.734. The median PFS of pts with an expression of PD-L1 <1% was 9 months (KI 6.4 – 11.6) and with an expression ≥1% 12 months (KI 9.8 – 14.2), also not being statistically significant with a p-value of 0.112. The blood parameters serum CRP, albumin and CRP/albumin-ratio had no significant impact on OS. This study showed that the assumption that lack of PD-L1 expression confers a favorable prognosis after radio-chemotherapy vs. PD-L1 expression ≥1% was not confirmed in our patient cohort.