People who scored 6 or higher on the 10-point scale developed in connection with the large, scientifically rigorous ACE (Adverse Childhood Experiences) study were twice as likely to develop cancer as people who scored 0. (I read this in a book by Bessel van der Kolk called
The Body Keeps the Score. A quick Google search turned up several studies, including this one:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3679131/)
As we all know, being told you have a deadly illness and then undergoing cancer treatment are, in and of themselves, traumatic. For people with a trauma history, a new adverse event can trigger anxiety, depression, PTSD, dissociation, depersonalization, etc. related to past trauma, making the whole thing doubly or triply difficult and trying. Think, for a moment, about what someone who's been sexually assaulted goes through in a CT machine.
And yet identifying and addressing trauma history is not a part of standard cancer treatment.
But you can seek it out. As a starting point, I highly recommend the book I mentioned in the first paragraph. Another very helpful book is Dan Siegel's
Mindsight.
Here's the short version: Mind/body dualism is not a helpful way to think about people. The human mind/consciousness is located in the entire nervous system, not just the brain. We are finely tuned sensing/feeling/judging/acting organisms. Our primary biological imperative is physical survival, so those systems operate automatically.
The fight/flight/freeze mechanisms that alert us to danger and keep us safe can get "stuck" in patterns that, over time, change our brains and our bodies on a cellular level in ways that damage our health. The good news is, contrary to what was once thought, the brain and nervous system can get reprogrammed/rewired.
Dr. van der Kolk talks about "top down" and "bottom up" approaches to reintegrating mind/body/spirit/thoughts/feelings. He is not opposed to psychiatric medications, and, as a psychiatrist, prescribes them, but in his book he points out the downside to relying on medication to control behavioral health. Medication can be very helpful, but it is not capable of making long-term neurological changes, but there are ways to do that.
He's convinced, after years of working with people who've experienced trauma, that the body has to be enlisted in the quest for mental health. I would add that we also need other people.
This can take many forms: yoga, martial arts, choral singing, dancing. Acting in a play (especially, he says, Greek tragedies), reciting poetry, praying, chanting are other ideas. Anything that increases mindfulness and strengthens the connection between the brain, the muscles, and the emotions can help. You can learn how to calm yourself down, focus, stay in the Now. You can interrupt a flood of adrenaline and other stress hormones with breathing techniques, visualization, affirmations, and other skills. As a bonus, this also helps with road rage, unreasonable bosses, and bratty children.
I personally think arts and crafts are therapeutic. Color. Knit or crochet. Embroider. Paint. Sculpt.
I also think beauty is healing. Get out in the sun, near water, with trees, grass, flowers, birds.
This post is already very long. But my point is the medical treatment you are getting is necessary, but probably not sufficient. You already know that in terms of diet and the need for physical activity. Your emotions, your thoughts, your mental state, are also things you can change for the better (with the help of a skilled therapist or a wise spiritual adviser). It may very well affect your cancer outcome. It will unquestionably help you live the best life you possibly can.