This is not secret, in fact it’s public knowledge that there are chemical compounds that they can give to rats and some other animals to give them cancer in mere weeks. “They” (Conspirators on US soil, or even Chinese, Indian or Russian generic drug manufacturers) could also put this in the medications received by specific groups of people that they wanted to have cancer in mere weeks. For example: Major drains on Medicaid, Medicare, even meds provided to specific cohorts of people on specific medications taking public support. Interesting. I wonder how those are regulated.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4949043/pdf/nihms-797149.pdf