Charities have criticised a proposal to block the routine NHS use of two drugs for advanced bowel cancer.
Bowel cancer is a major killer
The National Institute for Health and Clinical Excellence (Nice) said there was insufficient evidence to recommend Avastin and Erbitux.
But charities say both drugs are the best option for seriously ill patients whose cancer has spread.
They say the drugs have been shown to extend life expectancy by four to five months in some patients.
A similar decision has already been made in Scotland.
Bowel cancer kills almost 50 people a day in the UK. Each year, there are about 18,700 new cases in men, and nearly 16,200 cases in women.
It is easily treatable, but only if caught in its early stages.
Both the new drugs are monoclonal antibodies - the same type of new generation "biological" drug as the breast cancer treatment Herceptin.
Nice considered their use in patients whose cancer had spread, usually to the liver, but sometimes to the lungs. This is known as metastatic cancer.
Avastin, known technically as bevacizumab, works by starving cancerous tumours of blood, thus preventing them from growing in the body.
Research has shown it can extend life expectancy by an average of five months.
Lynn Novak, from Crawley, West Sussex, who has advanced bowel cancer, argued that Avastin had reduced the size of her tumours and helped to keep her alive.
However, the Nice decision could mean she will have to stop taking the drug, as she cannot afford to continue to fund it herself, having already spent thousands.
Her only hope is to convince her local primary care trust she is an exceptional case.
"I'm a different person, a different person. It's just given me a new life," she said.
"I was told I had six months to live in December 2005, but I'm still here, I'm back at work, I'm a productive member of society, and I feel really, really well."
Erbitux (cetuximab) works by blocking the proliferation of cancer cells, and is usually used after chemotherapy has failed.
In tests, it was found to extend life expectancy by at least four months for 50% of patients, and to shrink tumours by 50% in a quarter.
However, both drugs are relatively expensive. Avastin costs on average £16,824 per patient, and Erbitux £11,739.
Andrea Sutcliffe, Nice deputy chief executive, said the institute's investigations had found that neither drug represented a good use of "scarce NHS resources".
Andrew Dillon, the chief executive, admitted the drugs were of some benefit - but said there was uncertainly about how good they were compared with current standard treatments.
Television presenter Lynn Faulds Wood, who beat the cancer and set up the charity Lynn's Bowel Cancer Campaign, said the decision was "cruel" to patients.
Hilary Whittaker, chief executive of the charity Beating Bowel Cancer, said the decision was a "scandal" and the value placed on the lives of sufferers seemed to be "minimal".
"We are now the only nation in the EU not to offer cetuximab and bevacizumab to bowel cancer patients in the disease's advanced stages," she said, urging Nice to review its decision.
"We feel extremely disappointed that bowel cancer - the second biggest cancer killer - is not being given the attention or funding it deserves."
Ian Beaumont, of the charity Bowel Cancer UK, said: "NICE's negative decision with regard to the biological agents Avastin and Erbitux is further proof that the NHS is simply not working for bowel cancer patients and is overdue a full and comprehensive review."
Professor Karol Sikora, a cancer expert at London's Imperial Colllege, said: "These drugs are expensive but they are effective, trials have shown them to be effective.
"The difficulty for the NHS is they are costly. The way it is done is simply to calculate the amount of cost for prolonging survival by one year.
"The average NHS limit is around £30,000. That's what you and I are worth to the NHS for one year's extension of life."
Alan Maynard, professor of health economics at the University of York, said the problem was NICE was saying yes too much, adding to the financial pressure in the health service.
The Nice decision is now open to consultation before a final ruling is published in the autumn.
All three bowel cancer charities receive financial support from the drugs industry.