[fluidcruft]

Infectious diseases are different because they jump from host/reservoir to host/reservoir and can take their "experience" with them. Cancers spawn off from normal cells that mutate randomly. So the general scheme is that cancers (and each person's cancer's drug-resistance) develops from scratch in isolation within each person. Basically there's no real mechanism for one person's cancer to translate/share its experience against drugs with another person's cancer. Some cancers are related to viruses by increasing mutation rates which in turn increases the chance of a cancer developing. So basically I wouldn't expect overprescription to produce drug-resistance the way it can for anti-virals and anti-bacterials.