A case of dramatic reduction in cancer-associated thrombus following initiation of pembrolizumab in patient with a poor performance status and PD-L1

Pembrolizumab is a standard treatment for non-small cell lung cancer (NSCLC) with high-PD-L1 expression; however, its effect is dismal in patients with poor physical condition. Additionally, the effect of immunotherapy is generally limited in NSCLC harboring driver mutations such asEGFR, ALK, or RET gene aberrations.We report the beneficial effect of pembrolizumab in a patient with poor performance status and PD-L1+ lung adenocarcinoma with theCCDC6-RET fusion gene and co-occurring NF1/TP53 mutations, complicated by multiple cancer-associated thrombi and respiratory failure.Further studies are warranted to establish the role of co-occurring NF1/TP53 mutations as a positive predictive biomarker for pembrolizumab in NSCLC harboring RET fusion genes.