Sarcomatoid lung carcinomas show high levels of programmed death ligand-1 (PD-L1) and strong immune-cell infiltration by TCD3 cells and macrophages.

Objectives: Pulmonary sarcomatoid carcinomas (SC) are rare tumors, associated with worse prognosis and resistant to platinum-based regimens. Therapies targeting the PD-1/PD-L1 pathway are an emerging treatment for lung cancer. By characterizing intra-tumoral immune infiltration and evaluating PD-L1 expression, it could be possible to predict the efficacy of these new treatments.

Materials And Methods: From 1997 to 2013, data from all patients with SC who underwent lung resection was collected. Tumor-immune infiltration and PD-L1 expression were studied by immunochemistry tests, analyzing CD3 (clone SP7), CD4 (clone 1F6), CD8 (clone C8/144b), CD20 (clone L26), CD163 (clone 10D6), MPO (clone 59A5), and PD-L1 (clone 5H1). Results were compared to those of 54 NSCLC.

Results: In total, 75 SC were included. Forty (53%) SC expressed PD-L1 vs 11 NSCLC (20%) (p<0.0001). CD3+ tumor-infiltrating lymphocytes and CD163+ tumor-associated macrophages were more important in SC than in NSCLC (median 23% [17-30] of tumoral surface vs 17% [7-27], p=0.011 and 23% [17-30] vs 20% [13-23], p=0.002, respectively). In SC, the presence of Kirsten Ras (KRAS) mutations, blood vessel invasion, and TTF1+ positivity were associated with PDL1 expression. On multivariate analysis, only CD163+ macrophages and blood-vessel invasion were associated with tumoral PD-L1 expression. High levels of tumor-infiltrating lymphocytes (CD3+ or CD4+ and not CD8+) constituted a factor of good prognosis on survival. Interestingly, PD-L1 expression distinguishes subpopulations within tumor-infiltrating lymphocytes (CD3+ or CD4+) with different prognosis

Conclusions: PD-L1 expression was higher in SC than in NSCLC as well as immune-cell infiltration by TCD3 cells and macrophages. This suggests that targeting the PD-1/PD-L1 pathway could represent a new potential therapy.