in canada one of the first reasons they issued medical cards to patients was to help with this exact reason. they even named a strain chemo.
cannabis helps the user with hunger issues and also the sick feeling caused by chemo. it reduces the nausea and for many allowed them to continue eating and feeling much better after chemo than when they had not smoked or taken cannabis.
there is no final fact or fiction answer about this but there are results and stories from many different people and parts of the world saying that cannabis did in fact help.
israel has done a lot of research into cannabis maybe look at some of their studies.
i personally have helped many people both in canada and here in thailand who had different forms of cancers or tumors. not saying i cured anyone but there was real world results and stories from those people about how the cannabis had positive effects on their life.