RET fusions were recently identified in non-small cell lung cancer (NSCLC) and are considered as a potential therapeutic target of NSCLC. Sorafenib, a multi-kinase inhibitor, has potent anti-RET activity. We conducted a study to evaluate the efficacy of sorafenib in a small number of patients with RET fusion-positive NSCLC.

Eligible patients had advanced or recurrent NSCLC, were more than 20 years old, had undergone treatment with one or more previous chemotherapy regimens, had an Eastern Cooperative Oncology Group performance status 0-2, had adequate organ function, and provided informed consent. The presence of the RET fusion gene was confirmed by a split FISH assay. The patients were treated twice daily with 400mg of sorafenib taken orally. The treatment was continued until either disease progression or unacceptable toxicity.

From March 2012 to April 2013, three patients were enrolled. The responses to sorafenib included one patient with stable disease (SD) and two patients with progressive disease (PD). One patient took sorafenib for twelve months. The most common toxicities were palmar-plantar erythrodysesthesia syndrome, hypertension, and diarrhea.

Since sorafenib did not show dramatic responses, we suggest testing other RET inhibitors for the treatment of RET fusion-positive NSCLC. This study was registered at UMIN as trial number 000007515.