Internet is full of misinformation. From crackpot sites in allcaps with white text over a black background to very polished overhyped university press release with experimental treatments. Take all of them with a truckload of salt.
Start with some well known sources. I recommend:
https://en.wikipedia.org/wiki/Cancer
https://www.mayoclinic.org/diseases-conditions/cancer/sympto...
Then try to go deeper in the dark alleys of internet, but go with caution.
Some important points:
Cancer has a lot of variation. It's like putting all the viral illness in the same bag. A common cold is caused by a virus, ebola is caused by a virus, and there are a lot of other viral illnesses in between. Each one has a very different treatment and prognosis. Cancer is a very big bag of related illnesses, that may be very different. This comic is a good explanation about the problem with cancer http://phdcomics.com/comics.php?f=1162
In many case, the most important question is "primary or metastatic". Try to understand what this mean. Also a good comic about this is https://xkcd.com/931/ I think it's miss the cases where the first treatment is good for 5-10 years, and then it's possible to have a second treatment and get another 5-10 year, and if you are lucky get continue iterating.
