I can certainly see how one coiuld consider cancer to be parasitic in nature. However, cancer is not a parasite and neither is it caused by parasites (although the cellular damage caused by parasites could make one more susceptible to cancer). Sadly, I knew someone who believed that cancer was a parasite and treated it that way - and ended up dying as a result.

Like treatments that are effective for viruses, bacteria, and fungi - some items that are effective against parasites also have some effectiveness against cancer. However, cancer is not any of those. It is a cell proliferative disease which could be considered a cellular defense mechanism that results more than anything else from exposure to toxins.