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Treating prostate cancer that has recurred

If metastatic prostate cancer has recurred after surgery and other treatments, a way has been found to increase longevity while undergoing chemotherapy.

Principles of evolution and natural selection, and of game theory, have been used to drive a radical new approach to treating prostate cancer.

Oncologists typically treat aggressive cancers with maximum tolerated doses of anticancer drugs (the limit is there because these drugs also affect normal cells). From an evolutionary perspective, any cancer cells that survive the initial assault have traits that let them resist the drug. An alternative approach called adaptive therapy uses smaller doses that prevent the tumour from evolving total resistance. Tests show that the first round of treatment shrinks the tumour but allows a few cells that remain sensitive to the drug to survive. These cells keep rival, drug-resistant cells from taking over the tumour if it grows back. Subsequent rounds of treatment knocks the tumour size back down.

In this “game”, the oncologists are predators, and the cancer cells are prey. The oncologists’ objective is to kill the prey, or to at least keep it in check. But conventional cancer treatment shifts this balance. By giving a patient repeated strong doses of a cancer drug, the cells are pushed to evolve resistance.

When this occurs, the oncologists stop leading the game and instead have to keep up with an evolving, stronger cancer. By using the algorithm to deploy drugs more subtly, and closely monitoring what the cancer does in response, oncologists can stay ahead for longer.

In trials, this approach has doubled survival times in men with advanced prostate cancer.

See Scientific American, August 2019 “Darwin’s cancer fix” and New Scientist 10 March 2018 “Cancer algorithm uses game theory to double survival time”.