I didn't hear the NPR story, but studies can be halted when it's shown that the treatment is so clearly effective that it becomes unethical to continue administering non-treatments/weak treatments to your comparison groups. This usually indicates that research can and should advance to the next stage immediately.

Here's something to read on this (note the three criteria for a TL;DR): https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5024796/