My Dad was treated for colon cancer with 5-FU, and levamisole back in the 1990’s. Levamisole was used as a dewormer in sheep to treat fluke ingestion while grazing.
Whatever/however they found it was effective for colon cancer, I don’t know, but my Dad was about 25 years out from being cured of colon cancer, when heart issues took him from us.
His colon cancer was quite advanced when detected as well.
If these properties were known that far back, then why are we just now ‘discovering’ them as cancer fighting agents?.................