The part highlighted in red above is where the problems start. Cells, just like most other living things, will try anything to stay alive. When they are deprived of enough oxygen, they begin to use substitutes with glucose being the most accessible.
Although I'm NOT certain of the actual process (I'm neither an oncologist nor have I studied this area to the depths I've researched other things), but it's once it reaches the 40% tipping point that the cell begins to mutate. As Starise alluded to, there are usually other factors involved and, actually, this is one of the main reasons targeted, human-created treatments have issues: The body works synergistically, not as a bunch of separate functions.
Oxygen therapy is similar to the barometric treatment you get if you have the "Bends" (air-bubbles in your blood supply from surfacing too quick while deep-sea diving). The goal being to enrich the oxygen levels of the cells so they don't need to rely on sugars.
Currently, the so-called "treatments" for cancer are the equivalent of setting your house on fire to get rid of termites. There are two main reasons for all the celebration among cancer survivors: The first is the most obvious, to acknowledge those who have fought and won, but the second is to subtly imply that the treatments are effective so people will continue to use them. What they DON'T want the public to realize is that nearly 98% of those that take chemotherapy do not survive! (Here's one report: According to a 2004 report by Morgan, Ward, and Barton: "The contribution of cytotoxic chemotherapy to 5-year survival in adult malignancies. ... survival in adults was estimated to be 2.3% in Australia and 2.1% in the USA." See http://www.ncbi.nlm.nih.gov/pubmed/15630849, or https://www.burtongoldberg.com/home/burtongoldberg/contribution-of-chemotherapy-to-five-year-survival-rate-morgan.pdf)
Studies have also discovered that at least 80% of oncologists won't take chemotherapy for themselves should they contract cancer.
So, like the picture of the Centenarian smoking above, there's always going to be a few exceptions to the rule, however, if you only publicize the exceptions, the general masses (that typically do zero research) tend to assume that the exceptions are actually the norm. This is why, whenever you turn on just about any mainstream media currently, the news is almost always horrible. The reason is almost always a political agenda (I won't go down this path here, but it should be pretty obvious that governments like to create problems that they can solve by taxing and removing freedoms - money, power and control of the masses - same as it's been for millennia). One example was after marijuana was legalized in Oregon (2015). A news report trumpeted the 16 traffic fatalities caused by marijuana and driving!!! What they intentionally leave out is the fact that there were 13 traffic fatalities a few years earlier (2004) that involved marijuana - and this was before it became legal. What they also leave out is how that number compares to all traffic fatalities. For example, in 2016, there were 495 traffic fatalities in Oregon. One look at all the statistics and you could conclude that having only THREE additional deaths that involved (the now legalized) marijuana isn't really all that bad, and, how do we know that any of those wouldn't have occurred anyway if marijuana wasn't present? Needless to say, that's not the message those that control the media wanted to send!
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As a side-note on the original topic, the mind and body are incredible things! I've not only witnessed, but have had personal proof, that so-called "impossible" (per the mainstream medical society) things can occur. Intent is HUGE!!! My Mom flatly stated that she would beat her cancer and she was only one of two survivors for the type of ovarian cancer that she had (the survival rate was only 0.03%!!!). She's going on 91 in May and has been cancer-free for 22 years now. However, the bulk of her current health issues stem from the chemo treatments she had to take back then. The other main component (which applies to many areas of life) is KNOWING. This goes beyond belief. No, I'm not talking about Scientology or anything like that but, what I've found is that too many people feel that there's only one way to do things. I've realized that almost all of the different areas have something to offer, albeit sometimes buried in nonsense. There's a lot of good in both Eastern and Western medical philosophies, you just need to weed out the parts that are either added for "mystical/magical effect" or for profit (i.e., most of the prescription medication in Western medicine which, by the way, the physicians usually only learn about from pharmaceutical reps!). Remember: Your physician is NOT trained in the medicines they prescribe, pharmacists are.