For a long time cancer was thought to be caused by parasites, and indeed some forms of cancer are known to be connected to larval cyst infections today. In the past, treatment for parasitic infection and treatment for cancer were the same: chemotherapy.
Lately the broad spectrum anti-parasitics such as the bendazoles and ivermectin have been studied and found effective against a number of forms of cancer.
So the (previously debunked) parasite-cancer connection seriously needs to be revisited.

https://pmc.ncbi.nlm.nih.gov/articles/PMC3580766/