[peoplerock]

"once you've got cancer 'thinking positive' will probably do very little as you're too far gone" ?

I'll try to speak in an even-toned way (as spouse of a nine-year breast cancer survivor):

The survival rate is well over 50% (at five years) for many forms of cancer when treated with best current therapies. Most people who've got cancer are NOT "too far gone." In fact, therapists who specialize in such self-healing methodologies such as biofeedback would probably identify breast cancer patients (especially when caught in early-to-mid stages) as in a primo place to benefit from stress reduction, constructive visualizations of their future, and other audaciously positive thinking.

I would not expect "pressuring" anyone to think positively would be very therapeutic. However, skilled clinicians who guide patients toward their own preferred style of positivity can be god-sends. (In my/our humble experiences.)

[btilly]

The major flaw in your reasoning is that you've failed to identify a correlation between thinking positively and surviving cancer. Given that several large studies have also failed to show a correlation, I am forced to doubt the therapeutic benefits of positive thinking for cancer.

That is not to say that there are no health benefits from optimism. For instance there is evidence that it helps with the risks from cardiovascular disease. But it is far more dubious as a treatment for cancer.