Doctors have used a genetically engineered herpes virus to help treat patients suffering from mouth, neck and head cancer.

In a trial run by the Institute of Cancer Research (ICR) and The Royal Marsden NHS Foundation Trust, 17 patients were given injections of the virus, as well as being treated with chemotherapy and radiotherapy.

The cold sore virus, known as Onco VEX, was modified to multiply inside cancer cells but not in healthy ones. It would then burst and kill tumour cells, as well as releasing a human protein that would help stimulate patients' immune systems. The virus was injected into cancer-affected lymph nodes in up to four doses.

Tumour shrinkage could be seen on scans for 14 patients and over three-quarters of the participants showed no trace of residual cancer in their lymph nodes during subsequent surgery to remove them. More than two years later, over three-quarters of the patients had not succumbed to the disease.

'Around 35-55% of patients given the standard chemotherapy and radiotherapy treatment typically relapse within two years, so these results compare very favourably,' said Dr Kevin Harrington, Principal Investigator. 'This was a small study so the results should be interpreted with caution; however, the very high rates of tumour response have led to the decision to take this drug into a large scale Phase III trial.'