The most effective treatment for cancer is the surgeon's knife. A combination of surgery and radiotherapy ranks second in terms of effectiveness while chemotherapy - anti-cancer drugs - accounts for comparatively few cancer cures.
But surgery is effective only if the cancer cells have not spread around the body from the original tumour, in a process known as metastasis. Once a cancer has metastasised, then the prognosis is bleak.
It is here, in preventing tumours from metastasising, that British Biotech's new drug, Marimastat, offers most hope.
Dr Fran Balkwill, principal scientist at the Imperial Cancer Research Fund, said: "The long-term dream of this treatment is that you live with your cancer - you keep taking a pill and it doesn't spread. If your cancer is not spreading anywhere and not disrupting any vital function then it doesn't matter so much." But he emphasised that while "it's very interesting scientifically, these are very early data. We can't say this is a new cure for cancer".
Ann Barrett, professor of oncology at Glasgow University, was also cautious, but said: "Although overall, chemotherapy contributes in only a relatively small way to cures in cancer, a drug that could stop metastasis would be of interest and could be used in conjunction with the effective local treatments we do have - surgery and radiotherapy."
Marimastat's other significant potential benefit to patients would be that it can be taken orally, possibly at home, rather than having to be injected in hospital. It also appears to have fewer side-effects than existing anti-cancer therapies.
Current anti-cancer drugs attack and kill fast-dividing cells. Tumour cells grow quickly, but so does hair and the cells lining the gut - which is why people feel nauseated and suffer hair loss during chemotherapy.
Professor Gordon McVie, director of the Cancer Research Campaign, said Marimastat is "an interesting drug because it's got a new target". The drug obstructs powerful enzymes associated with tumours - matrix metalloproteases.
Dr Balkwill said that in epithelial cancers - for example those on the lining of the gut wall - there is a thin wall of collagen that can prevent the tumour spreading but these enzymes are breaking it down. If the tumour is to spread, it needs these matrix metalloproteases and other enzymes to get into the blood and circulate.
By concentrating on the body's mechanisms for containing the cancer rather than on killing tumour cells, Marimastat "has a completely different line of attack", he said.
British Biotech reported interim results on clinical trials of 94 patients with advanced colorectal, pancreatic, ovarian and prostate cancer. The company did not measure tumour shrinkage directly, instead it used a surrogate measure - the concentration of "cancer antigens" in the patients' bloodstream.
In 33 per cent of those taking the drug for 28 days, levels of antigen either fell or were stable. In a further 26 per cent, the levels rose but less quickly than before treatment started.
The company's research and development director, Dr Peter Lewis, said the tests needed to be completed before Marimastat was made available outside the company's trial programme.Reuse content