A treatment based on a common-cold virus has shown promise for inoperable skin tumours.
Surgery is the main treatment for melanoma, the deadliest form of skin cancer. In advanced cases where the disease has spread, going under the knife may no longer be an option, however.
Scientists from NYU Langone Health tested whether the common-cold pathogen coxsackievirus boosts the action of an immunotherapy drug, which helps the immune system detect and kill cancer cells.
An early stage clinical trial found injecting coxsackievirus along with the immunotherapy drug was well tolerated and shrunk melanoma tumours in nearly half of the 36 patients.
Eight (22%) entered complete remission within as little as two years, with no signs of skin cancer.
The results were presented at the annual American Association for Cancer Research meeting and are yet to appear in a peer-reviewed journal.
"Our initial study results are very promising and show this oncolytic virus injection, a modified coxsackievirus, when combined with existing immunotherapy is not only safe but has the potential to work better against melanoma than immunotherapy alone," said study author Dr Janice Mehnert.
Oncolytic viruses are a form of immunotherapy that uses the pathogens to infect and destroy cancer cells.
It has been evident since the 1800s that some cancer patients who endure infections experience tumour shrinkage. These infections were later tied to the pathogens that cause measles or herpes.
Genetic engineering allows scientists to re-tool viruses to target specific molecules on the surface of cancer cells, enabling the viruses to infect the cells more easily.
More than 16,000 people develop melanoma, beginning in the cells that control skin pigmentation, every year in the UK.
Immunotherapy may be administered if the cancer is stage four; when it has returned following treatment or spread to another organ.
According to the NYU scientists, immunotherapy is only effective in just over a third of melanoma patients.
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In the NYU study, the coxsackievirus drug V937 was injected along with the immunotherapy medication pembrolizumab.
Thirty-six men and women, most of whom were elderly, received the treatment duo every few weeks for at least two years.
Nearly half (47%) saw their melanoma tumours shrink, the results show.
Perhaps surprisingly, the patients who were least likely to respond to immunotherapy alone did best on the combined treatment.
The treatment duo was "well tolerated", however, more than a third (36%) had "serious immune reactions" in their liver, stomach or lungs. These side effects often occur with pembrolizumab, according to the scientists.
The team has stressed further research is required before the treatment duo becomes the standard of care for melanoma patients.
The next trial stage will be made up of melanoma patients with widespread disease, as well as those with tumours which if shrunk by the therapy, could be more easily removed by surgery.
It is also unclear how V937 changes the molecular make-up of the tissues surrounding tumours.
"Our goal is to determine if the virus turns the tumour microenvironment from 'friendly' to one that is 'unfriendly,' making the cancer cells more vulnerable to pembrolizumab," said Dr Mehnert.
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