A ketogenic diet or even a less restrictive lower carbohydrate diet can contribute to a slowing of the cancer growth for some cancers because cancer metabolizes

A ketogenic diet or even a less restrictive lower carbohydrate diet can contribute to a slowing of the cancer growth for some cancers because cancer metabolizes large amounts of glucose. But keep in mind that many cancer patients cannot afford to lose weight, which makes such dietary changes very difficult. The incredible stories that you hear are often true (stage 4 cancer remissions do occur) but usually involve selection bias. Usually it is hard to know what exactly worked, and it isn't going to work for everyone else. If you are interested in looking more deeply into complementary cancer treatments I would recommend looking into the work of Ralph Moss.