P2.04-59 Patient Survival in NSCLC Based on PDL1 Expression and Tissue Origin

Abstract

Patients with NSCLC who have high PDL-1 expression have favourable outcomes when treated with checkpoint blockade compared to those who don’t. Here we consider patient outcomes based on the origin of tumour biopsy and PDL-1 expression. This has not been widely considered or published. Patient tissues which were assessed for PDL-1 expression between 2013 and 2017 were identified using a central electronic pathology database. In addition, patients who were treated and tested locally between August 2015 and December 2017 were selected using an electronic chemotherapy database. A total of 422 patients were identified. Duplicates and patients who did not have enough cells for analysis (less than 100) were excluded from analysis. Individuals treated on clinical trials were included. Tissues were grouped into lung, lymphoid, pleural or other. Other included sites such as bone, cerebral or adrenal metastasis. Analysis was carried out using SPSS 25. Lung tissue: Patients with negative PDL-1 expression (n= 67) median OS was 619 days (95% Confidence Interval 428 -809 days). This included patients who were treated with EGFR and ALK inhibitors. In contrast, those who were PDL-1 positive (n= 106) and exposed to check point blockade, median OS was 511 days (95% Confidence Interval 373- 648 days). Lymph tissue: Patients who had negative PDL-1 expression (n= 21) median OS was 284 days (95% Confidence Interval 196 -361 days), compared to those who had high PDL-1 expression and managed with immunotherapy (n= 46) whose median OS was 546 days (95% Confidence Interval 128 -963 days). Pleural tissue: Tissues which were negative for PDL-1 expression (n= 6) median OS was 90 days (95% Confidence Interval 122- 477 days). Individuals who expressed high levels of PDL-1 (n= 15) median OS was 1253 days (95% Confidence Interval 642- 1864 days) for those who were exposed to immunotherapy. Other: In those with negative PDL-1 expression (n= 8) median OS was 1013 days (95% confidence interval 112- 1913 days). Patients with high PDL-1 expression and treated with immunotherapy had a median OS of 337 days (95% Confidence Interval 12- 661 days). OS was highest in patients who had high PDL-1 expression assessed in pleural tissues. In patients where PDL-1 expression was assessed in other tissues the worst outcomes were observed, possibly due to patient and disease factors. Some tissues may be PDL-1 rich or sparse based on origin. This may affect PDL-1 expression and subsequently patient outcomes. This warrants further investigation.