Prophylactic Swallowing Therapy During Head-and-Neck Cancer Radiotherapy: Effect of Service-Delivery Mode and Overall Adherence Level on Swallowing Function and Muscle Strength-the PRESTO Trial.

Only 115 of the 148 patients could be sorted into an adherence group, so a quarter of the sample was left out of the adherence analysis entirely. The adherence groups were created after the fact, not by randomisation. Patients who completed more exercises may differ in other ways that affect swallowing, and the study cannot separate that from the exercise itself. There was no group doing no prophylactic exercises, so the trial cannot show whether the exercises work. It can only show whether higher adherence goes with better outcomes. Follow-up stopped at three months, so nothing can be said about longer-term swallowing. Swallowing was assessed only with the MASA-C. No videofluoroscopy or endoscopy was done, so changes in residue or in specific swallowing movements could have gone unmeasured. No muscle composition was measured, so the researchers could not confirm that the muscle actually grew rather than simply working better. Strength rose sharply in the first week of training, which may partly reflect patients getting used to the devices, since no familiarisation session was used before the baseline measurements. The programme covered only the first 4 weeks of radiotherapy, shorter than in some earlier studies, by the team's own design.

The trial's funder is named as Kom op tegen Kanker, a Belgian cancer charity. The text supplied contains no competing-interest declarations for the authors, so nothing can be said from this paper about whether any author stood to gain from the device or the app.

Do not read the adherence result as proof that doing more exercise causes better swallowing. Patients were sorted afterwards by how much of the programme they completed rather than assigned to it at random, so the people well enough to keep exercising may simply be the ones who did better. Also do not tell patients the exercises will prevent their swallowing from worsening during radiotherapy, because it still worsened even in the high-adherence group.