LEICESTER, England -- Future cancer therapies could be tailored to suit individual patients, but because the drugs are so expensive and will have a limited market they may never be made.

There are already a few drugs on the market that target specific protein receptors in cancer and thanks to the decoding of the human genome more could be on way.

But an expert at Britain's Institute of Cancer Research warned on Tuesday that breakthroughs in research may not lead to new treatments because the costs will be too high for drug companies.

"This new treatment approach poses formidable problems for the pharmaceutical industry," Reuters quoted Dr.

Keith Snell as telling a science conference.

Personalized medicine, or pharmacogenomics, offers great promise to patients because the therapy is so specialized. But it costs about $100 million to develop a cancer drug and only about one in 10 drugs that are developed make it to the market, according to Snell.

Because they are targeted at specific molecules, the treatments would require sophisticated screening tests. The number of patients who would be treated with a particular drug would be confined to a small, genetically defined subgroup.

"What this means for Big Pharma is no more blockbuster drugs generating blockbuster profits. This is actually bad news for patients," Snell told the British Association Science Festival.

"If the potential market is too small there is no way the development costs of that drug are going to be covered by sales," he said, adding that pharmaceutical companies are already pulling out of oncology drugs.

A medicine which works in only two percent of patients currently has no chance of making it to market.

But if scientists can show it works in a certain genetic type it may win approval in future.

One way to reduce the cost of developing a new cancer drug would be to simplify clinical trials, which account for a hefty portion of the development costs.

Snell said another solution is for small biotechnology companies, major drug companies and scientific researchers to share the risks.

"They can all take on different facets of the whole development process and thereby, hopefully, try and make it an economic proposition," he said.

Snell warned that if the problem is not solved the chances of getting the newest cancer therapies to cancer patients who need them will be slim.