Non-Small-Cell Lung Cancer Patients with Coexistence of High PD-L1 Expression and RET Fusion-Which Path Should We Follow? Case Reports and Literature Review.

Pembrolizumab is widely used in first-line treatment in patients with advanced non-small-cell lung cancer (NSCLC) with high PD-L1 expression. The activity of pembrolizumab in NSCLC patients with rare molecular alterations is poorly characterised. RET gene rearrangements are identified in 1-2% of lung cancer patients. Here, we present two cases of RET -rearranged NSCLC patients with high PD-L1 expression (>50%), treated with pembrolizumab within routine clinical practice. Pembrolizumab was ineffective in both cases-single-agent immunotherapy seems to be of limited value in this group of patients. Selective RET-inhibitors, if available, are the optimal treatment for patients with RET fusion nowadays. The best sequence of the therapy is still not defined.