Yes vitamin C is beneficial to health and an effective addition to any natural cancer protocol. Vitamin C alone will not cure cancer. Cancer is a systemic disease that typically manifests in a weakened area or organ in the body. Environmental & dietary issues relating to cause need to be addressed.
Alkalizing and oxygenating the body are crucial to any successful natural cancer therapy & long term recovery.
You can't rely on mega doses of any supplement without addressing the whole body dynamic or environment that allowed the cancer to thrive in the first place. A cancer diet is crucial. Digestive enzymes are also crucial as well as an effective colon and liver cleanse. I highly recommend "Homozon" an ozonated, oxygen bonded colon cleanser. Vitamin C works very well in combination with Laetrile. Although the vitamin C needs to be in its whole form.
Here is an extremely interesting and shocking article on vitamin C and vitamins in general: http://www.shockinghealthnewsletter.com/blog/what-vitamins-are-good/