Learning From Evolution: A Gentler Approach On Cancer May Yield Better Results

Chemotherapy vials. Credit: National Cancer Institute

While aggressive anti-cancer treatment may seem appealing, some researchers are suggesting a milder approach could benefit some patients

Hang on, how can keeping cancer cells alive be a good thing?

While many people may think of a tumour as a homogeneous lump, there is usually a wide variety of cells within any cancerous population. These groups aren't exempt from evolutionary pressures, and certain cells can begin to dominate a tumour in response to challenge or adversity. This is similar to how bacteria evolve resistance to antibacterials. 

Getting rid of cancer as soon as possible is usually a top priority in treatment, and this is generally attempted with an aggressive course of chemotherapy at the highest dose possible. This is an overkill approach, aiming to totally overwhelm and destroy the tumour. 

Adaptive therapy

While this strategy works for some, just as taking a confrontational approach in diplomacy can often make things worse, intense chemotherapy can sometimes have the unfortunate effect of killing off all the 'gentler' cancer cells and leaving only the hardy, resistant ones. 

"There is a natural tendency to use high-dose therapy based on the assumption that each patient receives maximum benefit by killing as many cancer cells as possible. However, according to evolutionary principles, high-dose therapy is the least likely to be successful in controlling the tumour for any length of time because it intensely selects for resistant cells and allows them to grow rapidly because the treatment has eliminated all of their competitors"

This odd situation leads us to the counter-intuitive, but intriguing argument some scientists are now making - that we should instead be patient and seek to 'hem in' cancer instead.  

A controversial strategy

To test this theory researchers embarked on a series of experiments testing lower, adaptive doses of chemotherapy in mice with two different types of breast cancer. Reporting in the journal Science Translational medicine, they found that while all doses initially destroyed the tumour, continually lowering doses gradually enabled long term control of tumour growth best of all. Higher doses could destroy more of the tumour, but there was always a risk it could come back worse than before. The adaptive treatment was paradoxically the most effective at increasing survival rates. 

If you're scratching your head here, you're not alone. A deadly hammerblow would indeed make sense if you can ensure you've wiped out your opponent, but cancer is notoriously slippery and chemotherapy often spares the odd cell. Ignoring evolutionary patterns can actually cause greater long term harm in some cases. Farmers often retain a small region of any crop free of pesticides so that pests are unlikely to evolve to be resistant, and treating tumours gently may have a similar benefit. 

Pest management isn't so different from cancer therapy after all 

"People who do pest management are way ahead of those who do cancer therapy. I don’t think it’s unreasonable to think that eventually computer models can become highly prevalent for patients to help guide their treatment."

The novel approach uses algorithms and magnetic resonance imaging to respond intelligently after each dosing round - reacting intelligently to any developments. 

 

"We tend to think of cancers as a competition between the tumour and the host, but at the level of the cancer cell, cancer cells are mostly competing with each other"

This strategy won't work for everyone, but for especially unpredictable and dangerous cancers it could be a viable alternative. The researchers aim to test this adaptive therapy on prostate cancer in humans soon.

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