For six patients diagnosed with RET-rearranged NSCLC treated with RET inhibitors, we found available matched biopsies, including a RETi-baseline biopsy (before the start of the RETi, no more than six months before strating treatment) and a biopsy collected at the time of progression from RETi (RETi-PD). For all patients, we examined EGFR protein levels by immunohistochemistry (IHC) at RETi-baseline and after progression biopsies. This evidence concerns the gene RET and non-small cell lung carcinoma.