Dentist Mikhail Lvovsky describes his part in the trial of a new skin cancer drug
Scientists have presented results of an experimental new drug which in early stage trials has significantly shrunk skin cancer tumours.
US rearchers from Memorial Sloan-Kettering Hospital in New York said their results were "unprecedented".
While not a cure, the study of 31 patients with late-stage skin cancer suggested the therapy could improve the quality of life and extend lifespan.
Larger scale trials will now be needed to test the drug, PLX4032, further.
In the study, which has been unveiled at a major cancer conference in Berlin, researchers treated patients where cancer had spread throughout their system.
We've seen responses in patients who didn't respond to chemotherapy before
Dr Paul Chapman, lead researcher
They were given a new drug that blocks the activity of a gene thought to be involved in the spread of skin cancer, the so-called BRAF gene.
Within two weeks they noticed what they described as a "rapid and dramatic" shrinking of the tumours in the cancer patients:
Lead researcher Dr Paul Chapman said: "We've seen responses in patients who didn't respond to chemotherapy before. So far 70 per cent of patients have responded. So that is unprecedented for us."
New treatments can often seem promising to begin with - but have disappointing results in later larger trials.
However, the doctors involved in the trial - and those at the European Cancer Organisation who have organised the conference - have never seen a cancer drug act so quickly on such a high proportion of patients.
The drug, PLX4032, is the latest in a new generation of cancer drugs that block the action of cancer causing genes.
The most successful of these so far has been Glivec (imatinib), which is used to treat myloid Leukaemia and gastric cancer.
Professor Alexander Eggermont, president of the European Cancer Organisation, said: "The new drug is the equivalent of Glivec in terms of the effect it's having in advanced melanoma."
One of those to receive the treatment was Mikhail Lvovsky, a dentist from New York.
A year ago he stopped work because he was so ill. He asked his doctor to take him off his previous medication because he could not bear the side effects. Now six months after taking the new drug he is back at work.
He said: "The first thing I did six months ago was to call the funeral director and pay for my funeral. Now I'm thinking of going back to work. It's beyond exciting. It's fantastic."
Dr Lvovsky's cancer is so serious it is unlikely for the new treatment to hold it back for very much longer longer.
But if the drug is shown to be effective in larger trials it has the potential to help people whose cancer is less advanced to live healthier and longer lives.
Alexander Eggermont, president of the European Cancer Organisation, described the trial as "simply spectacular".
He said it showed the benefits of targeting treatment.
The news would transform melanoma work into "a very exciting field instead of a graveyard", he said.
Dr Toby Chave, a consultant dermatologist at Derriford hospital in Plymouth, said: "Up to this point advanced melanoma has been extremely difficult to treat and does not respond well to any existing chemotherapy or radiotherapy.
"Prognosis is very poor. The new study shows that there is some response to the treatment which is very encouraging. Even giving patients the hope of a few extra months of life is significant for them."
However Dr Chave stressed that the new treatment was not a cure.
He added: "Any hope of long-term cure for advanced melanoma is still a long way off."
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