Is selpercatinib effective in treating brain metastases in RET fusion-positive non-small cell lung cancer?

This study looked at the effectiveness selpercatinib (Retevmo) for the treatment of patients with RET fusion-positive non-small cell lung cancer (NSCLC) that has spread to the brain. The authors found that selpercatinib was effective in these patients. 

RET mutations are genetic abnormalities that can cause some types of cancer, including NSCLC. RET-positive NSCLC is difficult to treat and often spreads to the brain. RET mutations have been found in 1-2% of patients with NSCLC. 

Selpercatinib is a targeted therapy drug that blocks the protein coded by the RET gene abnormality. It has been shown to have good anti-tumor activity in patients with NSCLC. However, the effectiveness of selpercatinib in preventing further growth of NSCLC tumors that have spread to the brain has not been investigated. 

There were 80 patients with RET-fusion positive NSCLC that had spread to the brain involved in this trial. 22 patients had tumors in the brain that could be measured before starting the trial. 58 of the patients had non-measurable baseline spread of cancer to their brains. 56% of patients had previously received at least one treatment for brain metastases prior to starting selpercatinib. The average follow-up was 9.5 months.

In the 22 patients with measurable spread to their brains, the response rate was 82%. 23% of these patients had a complete response (complete disappearance of tumors). After 12 months, 55% of patients still had a response to treatment. The other 18% of patients had stable disease (the tumors did not grow or further spread). From the group with non-measurable brain disease, 34% of patients had a complete response.

The average length of time that all patients had without the further spread of their tumors was 13.7 months. 

3% of patients had side effects related to the treatment. Most severe side effects included elevated liver enzymes and high blood pressure. 

The authors found that selpercatinib was effective in treating RET-positive NSCLC that had spread to the brain. 

This trial was funded by Loxo Oncology, Inc, the manufacturers of selpercatinib. Most of the patients in this trial had previously received different treatments for brain metastases. This might have influenced the results.