How Much do Our Thoughts Affect Our Improvement from Sickness??

Some says its all about your immune response to your body that controls the spread of cancer to your body. They say if you have gone depression or you have generally gone through some difficult medical condition cancer cells seems to proliferate faster in us. Our immune response doesn't recognize the good and the bad cells anymore therefore they would allow cancer cells to grow and proliferate at a much faster rate than the normal cells. That is why there is no real cure on it but to re-educate our immune cells how to react to the bad cancer cells. That is where our scientist are still looking for a way to re-invigorate the immune cell and recognized by our immune system that cancer is a threat to our body and not allowed to proliferate in us. There is one study going on like the transfer factor that had been going on for quite sometime already. The thing is that I am just perplex that until now the medical community is not yet recognizing it as an alternative medication as against chemotherapy who is quite good in eliminating both the good and bad cells which eventually lead to many side effects that could lead to other opportunistic diseases to spread in our body.