stella
Lung CancerJuly 2021Summary reviewed May 2026

What the ARROW Trial Found — Pralsetinib for RET-Fusion Lung Cancer

ARROW tested pralsetinib, a daily oral targeted pill, in people with non-small-cell lung cancer carrying a rare RET gene fusion. Tumors shrank in 6 of 10 previously treated patients and 7 of 10 untreated patients.

What the trial was testing

The ARROW enrolled 590 patients with lung cancer. The study was sponsored by Hoffmann-La Roche and tracked outcomes across the full group of patients who matched the trial's eligibility profile.

It was an early-stage trial — researchers are still confirming safety and getting an early look at how well the treatment works. Trials at this stage are designed to produce evidence regulators and physicians can act on — not just observations to follow up later.

What the results showed

61-70% tumor response rates in RET-fusion lung cancer.

The Lancet Oncology · 2021 · NCT03037385

These findings — that tumor response rates in pretreated and untreated RET-fusion lung cancer — were published in the The Lancet Oncology and represent the headline result of the study.

Researchers tracked outcomes across 590 patients enrolled in the trial. The result was consistent enough across the group that the team felt confident reporting it.

What this means for patients

For patients with lung cancer, this result changes the calculus on what to ask their care team about. Whether it changes day-to-day care depends on factors like disease subtype, prior treatments, and where the patient is in their care journey.

What you can do now

Pralsetinib was originally FDA-approved for RET-fusion lung cancer but Genentech voluntarily withdrew the U.S. approval in 2024. Selpercatinib (Retevmo) is FDA-approved and available now for the same indication and is the standard targeted choice. Ask an oncologist about RET fusion testing if you have lung cancer.

Eligibility for the treatments mentioned above depends on specific test results and clinical history. Bring this summary, the trial name, and your most recent labs or pathology report to your next visit.