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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”.

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Opting for no prostate cancer medical treatment

This article is based on an article by Jill Margo in the Australian Financial Review on 24 May 2019 and my own experience.

When receiving a diagnosis of prostate cancer, some men elect to have no treatment. I know of one who did so, preferring to explore alternative therapies but without success. Anecdotally, after receiving the diagnosis some men never go back to their urologist. It took me nearly seven years to seek treatment after my first PSA test indicated a 50% likelihood that I had prostate cancer (which ultimately was confirmed and by then had spread to my pelvis).

For many men it is confronting to receive a diagnosis of prostate cancer. Some fear that incontinence and impotence will follow treatment – which it often does, at least for a period of time. Also, as with any surgery, removal of the prostate can have negative side effects.

Complicating matters, is the fact that it is currently difficult to predict which cancers will progress. Current estimates based on studies of large numbers of men indicate that 41% of prostate cancers are not destined to cause illness or death. Predictions for any one individual have a high degree of uncertainty and this is a major research topic.

A recent study interviewed eleven men who had biopsy-confirmed prostate cancer and all initially declined surgery or radiation. Most had felt pressured to have surgery and several had been told they would die without treatment – a prognosis that has not yet eventuated.

The psychological wellbeing of some was profoundly affected. Some had relationship breakdowns. Some sought alternative therapies. The careers of some were negatively impacted.

To doctors, the correct decision is not always clear and to reduce risk they sometimes recommend treatment even if there is a chance that it may be over-treatment.

Each man has to make his own decision, in consultation with the doctors and his family and friends.

Prostate cancer is a complex, confronting, and controversial disease. More research is needed to improve the quality of decision making.

My purpose in developing this website is to provide information and to raise money to contribute to the research and support needed to make better decisions.