Scientists have adapted a virus responsible for the common cold to treat lung cancer. The US-developed technique significantly reduces tumours and is applied by injecting the viral agent into patients. The treatment has already been so effective that it can be done on an out-patient basis. It is a highly advanced form of gene replacement devised by a team headed by Dr Jack Roth at the M.D. Anderson Cancer Centre in Texas. Genetic abnormalities in lung cells coincide with the existence of the cancer, and in many instances provide an early warning of its clinical form.
Dr Roth told the eighth World Conference on Lung Cancer at University College Dublin that the process involves identification of an abnormal cancer cell and correction of a gene known as p53. This, in turn, leads to tumour regression.
The virus that normally causes a cold is engineered so it cannot cause disease. It is injected, infects a cancer cell, repairs the gene and causes correct expression (or functioning) of gene p53. Further patient trials will be necessary with this promising treatment and to ensure it can be systemically successful.
An exact explanation of the immune system mechanism involved has yet to be established, but already it is clear that there is minimal toxic reaction in the body, Dr Roth said.
Between 10 and 20 genetic abnormalities can be found in a lung cancer tumour, according to Dr John Minna of the University of Texas South-western Medical Centre, whose research team first recognised the large number of genetic changes coinciding with lung cancer.
Its investigations are now concentrated on the significance of each abnormality - they can be due to gene mutation triggered by a carcinogen, such as smoke - to see if all are necessary for the cancer to occur.
These "markers" are tiny molecular changes that make early detection of the cancer possible. These often occur with a cell's DNA-repair mechanism, which determines its genetic code.
Examining the markers can also determine the extent to which a person has been exposed to smoke. These advances in molecular genetics, he said, would lead to dramatic treatment improvements in the form of vaccines, new drug combinations and gene therapy.
In addition, they would enable better evaluation of smokers likely to end up with the disease. He hoped research would focus on "families with multiple cases of lung cancer".
The genetic processes could also be used to develop better smoke-cessation strategies, more effective evaluation of people at risk, and to improve monitoring of former smokers. "Indications that the genetic changes persist in smokers for decades is absolutely frightening " because of lung cancer risk even after they give up smoking, Dr Minna said.
Treatment of lung cancer over the next 20 years "will become like breast cancer", he predicted, with screening of high-risk people.
