Cancer drug 'encourages tumours to grow faster'

Published on Sunday 22 March 2009 21:12

A CANCER treatment that starves tumours of blood can sometimes make the disease worse, researchers revealed yesterday.

Drugs called angiogenesis inhibitors prevent the growth of blood vessels that supply tumours with oxygen and nutrients.

However, new research, involving scientists in Glasgow and London, suggests certain types of this drug may actually promote the growth of tumours.

Some anti-angiogenesis drugs have already been marketed after proving their effectiveness in clinical trials.

These include Sutent, a kidney cancer drug, and Avastin, which is used to treat bowel, breast and lung cancer.

But the latest study, published in the journal Nature Medicine, focused on a treatment called cilengitide – an experimental angiogenesis inhibitor, which has not yet been licensed for patients.

The researchers, including scientists at the Beatson Institute for Cancer Research in Glasgow, found that, in laboratory tests, low doses of cilengitide had the opposite effect to what was expected – they promoted cancer growth.

Dr Andy Reynolds, from the Breakthrough Breast Cancer Research Centre at the Institute of Cancer Research in London, said: "Our study revealed a previously unknown mechanism through which drugs such as cilengitide behave.

"It showed that, while higher concentrations of cilengitide can block angiogenesis, lower concentrations can actually stimulate the supply of blood to the tumour and can promote its growth. These results may explain why initial results from early-stage clinical trials have not been as promising as hoped.

"Knowledge of this mechanism will help us develop new ways to make these drugs as effective as possible.

"In the future, we may be able to combine these inhibitors with other drugs to maximise their effectiveness for patients."

Dr Reynolds said the findings were "exciting" as they could help improve treatments for patients.

But he added: "Although we think that these results could be very important for patients, it's important to stress that most of this work has been done in a laboratory and not actually in people.

"It would be very interesting to know whether similar effects were taking place in people in the future."

Dr Lesley Walker, the director of cancer information at Cancer Research UK, said: "Drugs redirect the body's complex signalling systems.

"Sometimes, very subtle alterations to the way a drug is administered, or subtle changes to a drug's structure, can have a huge impact on its effectiveness.

"This study is important because it may help to explain the mixed results previously seen in patients and turn around disappointing results, so people may still benefit from the drug without the potential harm.

"Other anti-angiogenesis drugs like sunitinib (Sutent] and bevacizumab (Avastin] have proven effective enough for use in the NHS, but there is still need to understand why they can sometimes fail.

"It may be that there are similar mechanisms at work."