A medicine that was shown to improve the chances of surviving melanoma, one of the most aggressive forms of cancer, is no longer available to patients because its patent has expired, it has emerged.

Tests carried out at the VU medical centre in Amsterdam indicated that the injection, which boosts the immune system in the tumour area, significantly reduced the risk of patients dying or needing further treatment within 10 years.

Out of a test group of 30 patients who were given the experimental treatment a decade ago, two developed secondary cancers that proved to be fatal, while in a control group of 20 patients, six died and another three needed further surgery after their cancer returned.

Melanomas are fast spreading cancers that have a high rate of return, sometimes after a long period, meaning studies need to be carried out for several years. But by the time the effectiveness of the injection became clear drug manufacturers had stopped producing it because the patent had run out, meaning it was no longer profitable.

Immunologist and researcher Tanja de Gruijl said the pharmaceutical industry had stopped developing the medicine after a number of earlier tests produced negative results. ‘The industry loses interest when that happens,’ she told NOS Radio 1 Journaal.

‘But since then a new generation of medicines have come to market and we want to repeat these tests on larger groups of patients,’ De Gruijl added.

The number of melanoma cases in the Netherlands rose by 15% last year to 6787, compared to 1554 in 1990. Doctors say the rise is due to the growing popularity of sunbathing, as well as increased awareness of the condition. Around 800 people die each year as a result of melanoma.