Two research teams have produced ways of tracking the growth of cancer - and predicting if it is likely to return.

They could lead to treatment better tailored to each individual patient.

The first group, from the Peter MacCallum Cancer Institute in East Melbourne, used a type of scanning called positron emission tomography (Pet).

Unlike the normal x-rays and CT scans used to see how far tumours have spread, Pet scans can see inside the tumours to see how much cell growth activity is going on.

Many lung cancer patients whose CT scans suggested they had been cured were found to have living and growing tumours by Pet scans.

Likewise, some patients found to have a pronounced tumour on x-ray could be told that the mass was dead tissue after a Pet scan.

Patients whose tumours looked active under the Pet scan had four times the risk of dying.

Dr Harm van Tinteren from the Comprehensive Cancer Centre in Amsterdam said that Pet scanning might be able to determine which patients would be most helped by surgery.

"Pet more accurately shows the extent and stage of the disease."

Chemical markers

The other technique, developed by doctors at the Leicester Royal Infirmary, uses chemical tests to work out which lung cancers are the most dangerous.

Dr Giles Cox and his colleagues examined tumours taken from 168 patients, and looked for various proteins thought to be associated with more aggressive spread of the disease.

These included "metalloproteinases" (MMPs), which are involved in breaking down and rebuilding tissue so that tumours can spread.

They also looked at whether the lung cancer was growing its own blood supply - a process called angiogenesis.

From this they were able to accurately predict which of their patients would survive - and which would die.

Dr Cox said: "If the tumour had a high number of blood vessels, MMPs and growth factor receptors, then there was an 84% chance of cancer mortality in these patients.

"If a patient's tumour had none of these factors, the chance of death was only 36%.

"The prospect of treatment tailored to the individual patient, and to the individual tumour characteristics is possible."

Drugs are being developed which interfere with these chemicals, and so hopefully halt or slow down the development of the cancer.