A treatment breakthrough should mean many more people with bowel cancer can be cured, say experts.
The therapy can cure cancer
When caught early and treated, there is already a good chance of survival, but in some patients the cancer can return.
In trials, surgery combined with a new mix of chemotherapy drugs improved the chance of a complete cure by 25% compared to standard chemotherapy.
The data was presented by its Paris-based author at a European Society for Medical Oncology meeting in Vienna.
Bowel cancer affects about 38,000 people in the UK each year - mainly over 60s - killing about 14,000.
While it is obvious that picking up the disease and treating it as early as possible is the best way to ensure a cure, the success rates have not been high enough.
Dr Rob Glynne-Jones, Macmillan lead clinician at the Mount Vernon Cancer Centre in Middlesex, said: "This is the first time for years that we have had a major advance where patients are actually going to be cured."
He said for about 50 years there had been only one chemotherapy treatment available to treat bowel cancer, which was based on a drug called 5-FU.
Giving this treatment after surgery to remove the tumour reduces the risk of the cancer coming back by about 30%, he said.
In the trials on 2,246 patients with colon cancer, adding another drug, called oxaliplatin, reduced the risk by a further 25%.
Dr Glynne-Jones explained: "I know that may not sound very much, but when you think there are 38,000 patients getting colon cancer a year and probably 10 or 15,000 of them having chemotherapy afterwards, you are going to save quite a lot of lives.
"For the 30% of those who would have relapsed you are going to reduce that by a quarter. That's quite a big issue," he said.
He said adding in the extra drug did make the chemotherapy side-effects worse, but he said patients tended to accept that as a trade off for the increased likelihood of a cure.
In particular, the treatment can cause numbness or tingling in hands by affecting the nerve endings.
Oxaliplatin chemotherapy is available in some places in the UK.
The National Institute for Clinical Excellence is looking at its availability and is expected to make recommendations in May 2006.
The patients in the study all had stage three bowel cancer, which means the tumour is confined to the bowel and has not spread.
Author of the research, Dr Aimery de Gramont, from the St Antoine Hospital in Paris, told the Vienna conference the findings confirmed the importance of treating early with chemotherapy and surgery.
Jola Gore-Booth, chief executive of Colon Cancer Concern, said: "Lack of awareness is one of the main reasons colon cancer remains a killer.
"There is still considerable lack of knowledge and embarrassment surrounding this condition, which means that many people do not recognise the symptoms or do not act upon them.
"We need to get across the message that colon cancer is curable if caught through early diagnosis and treated appropriately, and encourage patients to act upon their symptoms as early as possible."