Remember the Borg on the Star Trek TV show? One reason they were such a formidable foe was that they adapted to attacks. When the Federation personnel from The Enterprise fired laser rifles a at Borg soldiers they are effective at first. Borg die, but the surviving ones learn from the loss and adapt to the laser gun, so they can survive the Federation attacks. The Federation adjust the frequency of their attacks and the Borg find a way to adapt to that tactic.
Cancer is similar. Many treatments fail because they effectively kill most of the malignant cells, but some survive – these cells are resistant to the drug – and when the cancer grows back and now most of the cells are resistant. Cancer is a dynamic ecosystem while the conventional treatment regimen is linear – a certain dose of a certain drug for a certain time.
Adaptive therapy is a program of chemotherapy where the type and dosage of drug changes in an attempt to fake out the cancer.
An article in the journal Cancer Research called adaptive therapy “evolves in response to the temporal and spatial variability of tumor microenvironment and cellular phenotype.”