My friend at American Cancer Society would take issue with that statement. He flies all over the world educating public health officials about how to fight tobacco use.
Tobacco by itself is a huge cause of preventable cancers.
The next big one is sun exposure, so ACS also promotes proper sunscreen use (and avoidance of tanning beds).
The ones caused by genes and random mutations are also a large percentage, but you can't teach people how to avoid those.
People should get radon tests in their home as well. Most lung cancer is either due to tobacco or radon.
After that, there isn't much advice specific to cancer: eat moderately and exercise.
https://www.ncbi.nlm.nih.gov/pubmed/20231499
https://www.ncbi.nlm.nih.gov/pubmed/20541680
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1694089/
Also, tobacco smoke seems to be an exceptionally weak carcinogen. It is near impossible to get it to cause cancer in animals (while eg, radioactive dust easily does so). Think about it, people expose themselves almost 24 hrs per day for decades and still less than 25% get lung cancer.
But by and large, it is a numbers / probability game. You could be exposed to a carcinogen routinely for your entire life and not have any problems. Or, you could be exposed once, and have it hit is just the wrong place. I'd say a 25% incidence rate is pretty high, and not something that I'd personally like to risk. Lung cancer rates are still high, with smoking being the primary risk factor. So, are you seriously going to argue that smoking is not something to avoid?
Skin cancer is another... the known primary risk factor is sun exposure (again, with a known mutational signature associated with UV light). Many people who avoid the sun likely already know that either a) they have a family history of skin cancer or b) they have sensitive skin that burns easily. Either of which is a good reason to avoid sun exposure.
Given the above and other comments in this thread, I'm struggling to figure out what your point here is. You keep attaching a lot of Pubmed links, but frankly, in this case at least, they aren't all that compelling and don't even begin to approach a scientific consensus. You're just cherry picking random articles.
Which of these statements do you find controversial?
1) Skin cancer rates are rising dramatically
2) Until very recently (in the last ten years) the vast majority of sunblock was transparent to UVA but opaque to UVB
3) Blocking UVB prevents the skins normal darkening and thickening response as well as sunburn
4) UVA penetrates the skin deeper than UVB and causes damage to the DNA in the cells there
5) Damage to the DNA of skin cells is associated with skin cancer
6) Without sunburn to warn people their skin is damaged they are more likely to leave their skin exposed to the sun.
This is classic confusion of correlation and causation.
People with lighter skin are aware of the increased risks of sun exposure and avoid/block the sun. Further, a lot of outdoor labor in the US is now done by people with darker skin (e.g. immigrants from Mexico with indigenous heritage).
Finally, sunblock isn't perfect. At-risk people can reduce, but not eliminate, the chances of developing a tumor. European-descended people are living in climates far south of where they evolved light skin, so cancer is inevitable.
> Also, tobacco smoke seems to be an exceptionally weak carcinogen
So is radon. What's your point? It may be weak, but it causes a massive number of avoidable tumors and deaths per year.
Broad spectrum sunblock may be less than perfect, but until recently all sunblock was transparent to UVA. It blocked UVB which prevented the natural sunburn/tan/thickening response without preventing the DNA damage.
Given the huge growth in skin cancers since people started wearing sunblock it seems likely that it was actively harmful for this reason.
There's HPV (human papillomavirus) that causes cervical cancer. It's preventable by a vaccine (e.g. Gardasil).
Helicobacter Pylori can cause stomach cancer. If detected early it can be eliminated with a two week antibiotic treatment.