[benjijay]

It's been a few years since I was as deep into this realm so I might be slightly off but;

Cancers and Tumors mostly happen as a result of some errant mutation - there are limitless causes for such things and the best diet in the world can't save you from random biological chance or solar radiation. Everything comes with a risk and 98 times out of 100 your own defences will see this mutation happen and shut it down before it gets too far

A 100% effective 'prevention' for cancer would basically be a souped-up immune system to the point that we basically never get meaningfully sick, and probably live another 30-50 years as a result (most cases of "died of old age" are more like "had 7 different minor cancers which overwhelmed the body's systems")

[chefandy]

Yeah— it's obviously worth interrogating how our environments affect our cancer risk, but considering that the disease was named by Hippocrates in the 300s BCE, it seems pretty unlikely that any single avoidable environmental factor could be "the cause," or any single factor could be "the mechanism."

[benjijay]

Certainly there are myriad 'causes', and likely at least a few mechanisms if you get into specifics, but as a general rule a cancerous tumour is a group of cells that multiply faster than they die (or don't die at all), and consume resources without 'giving back' to the organ in which they reside - effectively the "I have outlived my designated usefulness" switch gets commented out and replaced with "multiply even harder, forever"

[stvltvs]

A non-specific treatment that revs up the immune system increases the risk of autoimmune disease. It would have to be specific to the cancer AFAIK, so more of a treatment for an existing cancer than a preventative measure.