Meditation short circuits that stress.
One of the Buddha's Four Noble Truths, the first one, is that "life is suffering". According to the Buddha, life is suffering because of "old age, sickness and death", but also because of many subtle day-to-day discontents such as not having what we want, having to put up with what we don't want, and the subtlest one of all, being aware, even when we are happy, that the happiness won't last. But the Buddha might as well have said "life is stressful," because that would have been just as true.
Meditation was one of the Buddha's psychological remedy for the pain of the First Noble Truth. Meditation teaches you to live in the now. Regretting the past or dreading the future take up huge amounts of mental and physical energy. Every moment of living in the now is like a vacation from regret and dread, freeing up energy for healing, creativity and resilience. The peace of living in the moment without fear floods your bloodstream with positive hormones. It gives your body a rest.
Cancer can fill you with fear of the future and regret for the things that you have not done in the past. Meditation teaches you how to stop those thoughts. Fear in particular constricts you -- it makes your breathing shallow, so you don't get sufficient oxygen (and cancer thrives in an anaerobic environment). It constricts your mind too, so you become trapped in a circuit of negative thinking. Negative thinking in turn floods your body with stress hormones -- which cancer also loves.
One type of meditation I have done is called Radiant Mind. We were shown on a very vivid graph how everything happens in the moment. Your mind might travel back with memories or forward in anticipation or dread, but it still resides here, in the moment. Everything you experience in your mind affects your body. The quality of your life, and to a large extent the health of your body, depend on how you feel in the moment, and it is from moment to moment to moment that the tenor of your life is determined. One exercise we were taught was to stay in the moment, accept everything in the moment, observe everything in the moment and let everything go, moment to moment.
Another type of meditation I learned is Mahamudra. In Mahamudra you calm the mind by focusing on the breath, and then you ask "where is my mind? what shape is it? what size? what colour?" You discover that's it's nowhere and everywhere, that is has no shape and no colour, and that it is not you. There is more to you than your mind, more to you than your body, more to you than your self, more to you than your pain. You can wedge some breathing space between yourself and your pain, yourself and your fear, by looking at them as an impartial observer.
If you can learn to become that impartial observer called "awareness", and so stop identifying with your body, with your fear, with your pain, you will have won an important battle in your quest for health. Alastair Cunningham, the creator of the Healing Journey, recognized this and made meditation one of the cornerstones of his program. Many graduates of the program fared much better with their cancer than their diagnoses suggested.
Meditation resources abound. There are CDs, DVDs, local meditation centers and teachers, Buddhist temples both of the Zen and the Tibetan variety, and Youtube videos galore. I would in particular recommend Adyashanti's teachings. But there are many others, Eckhart Tolle, Deepak Chopra, Pema Chodron, Joseph Goldstein, Jack Kornfield, Ram Dass, Thich Nhat Hanh. Find one who speaks to you.
Postscript January 19: Just found this article on a cancer survivor who partly credits the Healing Journey program for her healing.