Pralsetinib in patients with RET fusion-positive non-small cell lung cancer: A plain language summary of the ARROW study

What is this summary about?This is a summary of a research study called ARROW, which tested a medicine called pralsetinib in patients with non-small cell lung cancer (NSCLC), thyroid cancer, and other advanced solid tumours caused by a change in a gene called RET. For the purposes of this summary, only patients with NSCLC with a change in RET called fusion (RET fusion+) are highlighted.What were the results?In total, 281 patients with RET fusion+ NSCLC had taken part in this study across the USA, Europe, and Asia. Patients were asked to take four pills (adding up to 400 mg) of pralsetinib each day and were checked for any changes in their tumours, as well as for any side effects. After an average of 8 months of treatment with pralsetinib, 72% of previously untreated patients and 59% of patients who had previously received chemotherapy had considerable shrinkage of their tumours. Among 10 patients with tumours which had spread to the brain (all of whom had received previous treatments), 70% had their tumours shrink greatly in the brain after treatment with pralsetinib.On average, patients lived with little to no tumour growth for 16 months. In previously untreated patients, the most common severe side effects that were considered related to pralsetinib treatment were decreased white blood cells (neutrophils and lymphocytes), increased blood pressure, and an increase in a blood protein called creatine phosphokinase. In previously treated patients, the severe side effects were decreased white blood cells (neutrophils, lymphocytes, and leukocytes), increased blood pressure, and low levels of red blood cells. In both untreated and previously treated patients, the most common severe side effects that required hospital attention were lung inflammation/swelling causing shortness of breath (pneumonitis) and lung infection (pneumonia).What were the results? In total, 281 patients with RET fusion+ NSCLC had taken part in this study across the USA, Europe, and Asia. Patients were asked to take four pills (adding up to 400 mg) of pralsetinib each day and were checked for any changes in their tumours, as well as for any side effects. After an average of 8 months of treatment with pralsetinib, 72% of previously untreated patients and 59% of patients who had previously received chemotherapy had considerable shrinkage of their tumours. Among 10 patients with tumours which had spread to the brain (all of whom had received previous treatments), 70% had their tumours shrink greatly in the brain after treatment with pralsetinib. On average, patients lived with little to no tumour growth for 16 months. In previously untreated patients, the most common severe side effects that were considered related to pralsetinib treatment were decreased white blood cells (neutrophils and lymphocytes), increased blood pressure, and an increase in a blood protein called creatine phosphokinase. In previously treated patients, the severe side effects were decreased white blood cells (neutrophils, lymphocytes, and leukocytes), increased blood pressure, and low levels of red blood cells. In both untreated and previously treated patients, the most common severe side effects that required hospital attention were lung inflammation/swelling causing shortness of breath (pneumonitis) and lung infection (pneumonia).What do the results mean?Overall, the ARROW study showed that pralsetinib was effective in shrinking tumours in patients with RET fusion+ NSCLC regardless of previous treatment history. The recorded side effects were expected in patients receiving this type of medicine. Clinical Trial Registration: NCT03037385 (ARROW) (ClinicalTrials.gov)