This approach could give us many new diagnostic tests within three to five years

Professor Mark Rubin, University of Michigan

Often, an uncertain tactic of "watchful waiting" is employed, with frequent checks to see if the cancer is growing fast, but this can be disconcerting for patients who have been told they have cancer but are receiving no treatment.

The latest research, published in the journal Nature on Thursday, looked at prostate samples from 50 men.

Malignant tumours had large numbers of genes which varied from normal prostate tissue, they found.

Researchers then compared tissue from localised, non-spreading prostate tumours, and tissue from aggressive, spreading cancers.

They found two new genes which appear to have a role in the development of the cancer - higher levels of gene expression in the tissue were associated with a worse prognosis for the patient.

Spotting the difference

Professor Mark Rubin, from the University of Michigan Medical School, said: "The ultimate goal is to help physicians determine which patients need to immediate, aggressive treatment and which can be watched and treated conservatively.

"This approach could give us many new diagnostic tests within three to five years.

"Eventually, it could lead to a diagnostic kit physicians could use to determine the best treatment and prognosis for their patients with prostate cancer."

Molecular profiles give much more specific information on the stage of a tumour than can be gained using conventional diagnostic techniques

Cancer Research Campaign spokesman

Although prostate cancer, in which doctors face a choice between radically different treatment strategies, is an obvious choice for "tailored treatments", other researchers are hopeful that the genetic makeup either of the individual, or, more particularly, of the tumour, will be key to treatment choice in various cancers.

A spokesman for the Cancer Research Campaign said: "Molecular signatures have the power to reveal exactly which genes are switched on and which are switched off in a cancer.

"We already know about some of the key cancer genes. Molecular profiling is throwing up new genes and understanding their function is the next step.

"The short term benefits locked up in genetic signatures lie in diagnosis - molecular profiles give much more specific information on the stage of a tumour than can be gained using conventional diagnostic techniques.

"And this means doctors can better tailor treatment to individual patients. In the long term, genetic signatures are also throwing up new leads for anticancer drug design."