Cloud services provided over grid technology are helping to treat cancer patients, owing to an enormous effort by European researchers working closely with industry. Cancer is Europe’s second largest killer and one of the most difficult diseases to treat. There are dozens of therapeutic protocols designed to respond to the vast diversity of cases that confront doctors. Radiotherapy has proven a particularly effective treatment. Here a linear accelerator, or Linacs in the jargon, attacks the cancer directly by delivering radiation from several directions. But treatment is complex. The direction, size and duration of dosages are all tailored to each case, and must be recalculated every time via simulation. It is a phenomenally complicated computation, requiring lengthy processing time, so much so that it can mean delays and this has the knock-on impact of lowering the number of patients who can be treated by each Linacs machine. Faster diagnoses would help, but the required computing power is expensive, dramatically increasing the Linacs installation and operation costs. It is a critical bottleneck.