By Fergus Walsh BBC News, medical correspondent

Peter Kenning will be closely monitored in the months ahead Peter's treatment

It's just twelve weeks since Peter Kenning was told he had neck cancer.

Radiotherapy and chemotherapy have already helped to shrink the tumour.

But he is also receiving an entirely new treatment.

It's a genetically modified virus which has taken a decade to develop and is being injected directly into the cancer.

Mr Kenning says he was initially apprehensive about getting an experimental treatment.

"I was concerned, but the Marsden gave me lots of information and my fears were soon allayed.

"From a personal level I feel fortunate to be getting it, and anything that will help to future research has got to be a positive thing."

Cold sore virus

The doctors at London's Royal Marsden Hospital and neighbouring Institute of Cancer Research are trying to harness the destructive power of a virus to seek out and destroy tumours.

They use a herpes virus - which usually causes cold sores.

It is genetically modified to be attracted to growing cancer cells, but not able to infect normal tissue.

The virus gets into the cancer cells and once inside, replicates until the cells burst.

We think this is enormously exciting opportunity to bring virus and gene therapy into front line treatment of cancer Researcher Dr Kevin Harrington

But the virus particles also carry an extra bit of genetic material which produce bio-markers designed to make the tumour visible to the immune system.

So does it work? Well in laboratory and animal trials it was certainly effective and there've been no ill effects in the handful of patients treated so far.

Scientists at the Institute of Cancer Research developed the vaccine and are convinced this could be a unique approach to fighting cancer.

Dr Kevin Harrington, who's leading the trial says: "We think this is enormously exciting opportunity to bring virus and gene therapy into front line treatment of cancer combining it with treatments which offer cure but attempting to improve the cure rate when combined it with chemotherapy and radiotherapy."

Peter Kenning will be closely monitored in the months ahead as will patients on several other early stage trials - using viruses to target breast, lung and several other common cancers.

This trial at the Marsden is just one of a host of projects utilising the power of gene therapy to tackle cancer.

And with 70% of the UK's gene therapy trials targeting cancer, this novel approach represents a radical new frontier in the fight against this age old disease.