‘Drug holidays’ beat cancer drug resistance in mice

The animals had melanoma, which can rapidly become resistant to treatments. However, a study in the journal Nature showed tumours also became dependent on the drug to survive. Withdrawing treatment caused tumours to shrink.
Experts said the findings were exciting, but still needed testing in people. A team of scientists at the University of California, San Francisco, the Novartis Institutes for Biomedical Research, California and University Hospital Zurich, in Switzerland, were investigating how melanoma cells became resistant to a drug, vemurafenib.
The drug can slow the progress of a tumour in the short-term, but it soon becomes ineffective with deadly consequences. The tumours gain resistance by changing the chemistry of the inside of a cell. However, the researchers showed this process left the cancer cells dependent on the drug – like an addict.
When the mice were no longer given the drug, the tumours began to shrink. The scientists used this knowledge to test a new way of prescribing the medication. Instead of giving the drug every day, the mice were given drugs for four weeks and then had a two week "drug holiday" before starting the pattern over again.a