Nutrition
IV nutrition can help cancer patients maintain or gain weight and prevent muscle breakdown during and after cancer treatment.
Quality of life Some studies suggest that IV vitamin C can improve the quality of life of cancer patients, including reducing pain and the need for analgesics.
Cancer cell proliferation Laboratory studies have shown that IV vitamin C can decrease cell proliferation in cell lines from a number of types of cancer, including prostate, pancreatic, hepatocellular, colon, mesothelioma, and neuroblastoma.

The immune system keeps track of all of the substances normally found in the body. Any new substance that the immune system doesn’t recognize raises an alarm, causing the immune system to attack it. For example, germs contain substances such as certain proteins that are not normally found in the human body. The immune system sees these as “foreign” and attacks them. The immune response can destroy anything containing the foreign substance, such as germs or cancer cells.

The immune system has a tougher time targeting cancer cells, though. This is because cancer starts when normal, healthy cells become changed or altered and start to grow out of control. Because cancer cells actually start in normal cells, the immune system doesn’t always recognize them as foreign.

maintain or gain weight and prevent muscle breakdown during and after cancer treatment. 
Quality of life
Some studies suggest that IV vitamin C can improve the quality of life of cancer patients, including reducing pain and the need for analgesics. 
Cancer cell proliferation
Laboratory studies have shown that IV vitamin C can decrease cell proliferation in cell lines from a number of types of cancer, including prostate, pancreatic, hepatocellular, colon, mesothelioma, and neuroblastoma.

Clearly there are limits on the immune system’s ability to fight cancer on its own, because many people with healthy immune systems still develop cancer:

• Sometimes the immune system doesn’t see the cancer cells as foreign because the cells aren’t different enough from normal cells.
• Sometimes the immune system recognizes the cancer cells, but the response might not be strong enough to destroy cancer.
• Cancer cells themselves can also give off substances that keep the immune system from finding and attacking them.