You are right - cancer does suck - but the OP is correct to ask for quantitative information.
As someone with a brother whos busy dying of stage 4 esophagus cancer, I can assure you there is an unlimited amount of bullshit theories and unsubstantiated therapies out there.
My brother's been strict keto since the initial diagnosis (against his doctors advice) due to various videos on places like diary of a CEO, and has also had unqualified but all knowing diet advisors having him take various green juices, and enough herbal supplements to choke a horse, all at the expense of him being able to get actual nutrition in while his capacity to actually eat solid food rapidly declines due to the cancer choking off his esophagus.
Now he is spending hugely to do hyperbaric treatment, red light therapy, vitamin C injections, deep heat thermal pad treatment, and any other therapy that they push his way with clinics that only have online doctors and questionable qualifications.
I would a few good sessions at the gym to be the cure, but there needs to be actual data backing it, especially considering the multiple surgeries and compromised abdominal muscles and hernias etc from all the laparoscopic examinations and other medical procedures that patients like my brother have already been through. He was a 6'6" 130 kg fairly athletic guy, whos now down to 76 kg over 10 months and for the doctors have told him he shouldn't be lifting anything heavier than 5kg.
All those diets pills, potions and vitamin c / d / whatever injections don't seem to be stopping the cancer yet, even though the people pushing them all reckon it's the one true cure. I drew the line at him chugging blended apricot kernels or the poor bugger would have ended up giving himself cyanide poisoning.
I do notice clinics like "hope for cancer" aren't offering a money back guarantee to your estate if it turns out their miracle 50k to 100k treatment doesn't keep you alive for at least 5 years though.
Testimonials about some therapy aren't sufficient - dead people don't leave testimonials saying the treatment didn't work.
Alternative therapies need actual data to back them, or they are bullshit.