A radical approach to cancer treatment which keeps tumours under control rather than destroying them completely may be more effective than conventional therapies, scientists say.

The idea draws on Charles Darwin’s 150-year-old theory of evolution and recasts tumours as diverse ecosystems of cells which can be manipulated to prevent them from growing out of control.



The strategy is highly experimental and has only been tested in mice, but successful trials in humans could usher in a transformation in cancer care, where patients live healthy lives with tumours that are constantly kept in check by low doses of medicine.



Routine cancer treatment assumes that patients do best when a therapy kills off the maximum number of malignant cells in their bodies. But tumours are collections of different cells and some are more resistant to drugs than others. A dose of chemotherapy will typically leave drug-resistant cells behind. Unencumbered by their neighbours, they can rapidly grow back when the treatment stops.



Scientists in the US wondered what would happen if anticancer drugs were used to shrink tumours without destroying the diversity of cells inside them. They hoped that the surviving cancer cells would stop more aggressive, drug-resistant ones from taking over, just as grass can prevent moss running wild in a garden.



Writing in the journal Science Translational Medicine, Robert Gatenby at the H. Lee Moffitt Cancer Center in Tampa, Florida, describes how his team tested the idea with the chemotherapy drug paclitaxel (or taxol) in mice with two different forms of breast cancer.



When the mice were given standard chemotherapy, their tumours shrank, but grew back as soon as the treatment ended. For the new therapy, mice were given initially high doses of drugs followed by ever lower doses. The strategy appeared to be more effective than standard treatment. Giannoula Klement, a cancer specialist at Tufts University School of Medicine in Boston, who was not involved in the work, said that in about 60% of the mice, the cancer treatment could be withdrawn completely with no further growth of the tumours.



In an accompanying article, Klement argues that to beat cancer, it must be considered as an ecosystem of different cells. “The likelihood that a ‘magic bullet’ against cancer is going to be found is nil. If we have learned anything from the eco-evolutionary model it is that unless we respect these eco-evolutionary laws, we will continue to play a cat and mouse game with cancer,” she writes.



Instead of eradicating cancer, the new goal for doctors needs to be prevention of cancer disease, she adds. “We need to stabilise tumour growth and enable gradual, controlled regression over time.”



Charles Swanton, a scientist at the Francis Crick Institute in London, who is part-funded by Cancer Research UK, said: “How cancers become resistant to treatment has been one of the greatest challenges facing doctors and their patients. This work tries to find a way around a phenomenon known as ‘competitive release’, where drug resistant cancer cells survive and take over the tumour once the drug-sensitive cells have been killed off.

“When this happens in cancers, the disease is often much harder to treat due to the limited number of drug options available. This new approach is looking into how to reverse this by using different schedules of chemotherapy to keep some of the drug-sensitive cancer cells alive to outcompete the resistant untreatable cancer cells. Although this has work has been done in mice, it shows promise and paves the way for clinical trials with new dosing schedules in patients.”

Rachel Rawson, a senior clinical nurse specialist at Breast Cancer Care, said: “The potential to reduce gruelling side-effects of chemotherapy, while increasing the treatment’s effectiveness, could dramatically improve the lives of people with breast cancer. This is an exciting avenue to explore. Chemotherapy can mean women live with debilitating sickness, fatigue and extremely distressing hair loss for many months, making every day a challenge.



“However, there remains a long road from this study on mice to any potential changes in clinical practice. And we want to reassure anyone concerned: the treatment currently out there has been successfully trialled on thousands of patients.”

