https://www.thelancet.com/journals/lancet/article/PIIS0140-6...
The study was designed to show non-inferiority, which doesn't preclude their ability to show an improvement. It would be helpful to see other studies before determining that proton therapy is better (or even non-inferior) to radiation therapy. It's certainly much more expensive, which shows up in the study as many subjects being denied insurance coverage.
Edit: This is now in the weeds, but the per-protocol participants didn't fare better than the intention-to-treat participants, which one might expect since insurance approval lead to dozens of subjects changing treatment arms.