Success rates in cancer are usually broken down by type of response (complete, partial, no growth, no response) and stage. It would have been helpful for the article to say what stage was being treated and compare the response rates in that stage to the best available treatment. For some cancers, 80-100% rate of complete response is currently achievable. Some are at 0%.

>their illness was well advanced and considered untreatable

Seems the 25% is up from a perceived 0% possible success rate.