Seriously ill patients are said to have seen "spectacular effects" after receiving the medication which could be used to combat other forms of the condition.
It is the first time scientists have come this close to providing a remedy for advanced melanoma.
The news will bring hope to thousands of people who are diagnosed with skin cancer in Britain each year.
Until now the prognosis for advanced melanoma has been very poor and many patients die within months of diagnosis.
Professor Peter Johnson, chief clinician at Cancer Research UK, said: "We're just at the beginning of a new era of cancer treatments using the immune system. These drugs that can turn the body's own defences against a tumour are starting to show real promise for melanoma and other types of cancer."
The new cure contains two types of drug - ipilimumab (known as ipi) and anti-PD1s which break down the defences of cancer cells and are still in clinical trials.
Doctors can reboot a patient's immune system by combining the two.
One in six patients are already being saved by the ground-breaking treatment, the European Cancer Congress has been told.
A new combination of drugs could mean more than half are cured of the deadly condition.
Professor Alexander Eggermont of the Institut Gustave Roussy in France said: "Advanced] melanoma could become a curable disease for perhaps more than 50% of patients within five to 10 years."