Prof Ashworth said that understanding of how different cancers were caused by different genetic triggers was building “incredibly rapidly”.

Genetic profiling of tumours is already used to some extent, but current methods only look for a few genes. Women with advanced breast cancer are tested to see if their tumours have a particular variant of the HER2 gene, which causes a fifth of cases. Those with it are given Herceptin, but the same drug would do no good for those without the gene variant.

Advanced melanoma patients with a particular gene mutation are prescribed Vemurafenib, a pill that has been shown to increase survival, on average, from 9.6 to 13.2 months, and help patients feel much more energetic.

But average survival times hide massive variations. One patient at the Royal Marsden in Chelsea, where the institute is based, has survived 10 years so far with advanced breast cancer on Herceptin.

Prof Ashworth said that such cases were the exception.

But he added: “We would hope that they will become the norm. By actively profiling patients who respond well, and sequencing their genomes, we can find the genes that are responsible for that.”

The institute wants to build a DNA database to identify lots of genes responsible for cancers. It is launching a three-year, £3 million project called the Tumour Profiling Unit to advance knowledge of the genetic profile of cancer.

Prof Ashworth said: “None of this is science fiction. One would think in five or 10 years this will be absolutely routine practice for every cancer patient.”

He thought the method would have “a big impact” on a range of cancers within a decade, but added: “Over the next two to three years, there will be individual patients who receive substantial benefits from these technologies.”

He also thought genetic profiling would make developing new drugs quicker and less expensive.

But tumours can sometimes develop resistance to drugs in months.

Scientists hope to counter this by monitoring tumour DNA. Currently, this requires repeated biopsies, which are invasive. Scientists at the institute are developing a blood test to examine free-floating DNA from tumours instead.

Prof Ashworth admitted that personalised cancer medicine was in its “early days”. Resistance to drugs was a major obstacle, he said. “People have described this as a game of whack-a-mole – you knock one on the head and another comes up,” he said.

“But this isn’t black magic. The knowledge is accumulating incredibly rapidly. Despite the setbacks, most people are optimistic.”

One implication is the use of drugs designed for one cancer on a different type, if they share the same genetic cause.

Charlotte Beardmore, of the Society and College of Radiographers, described personalised cancer drugs as a “fantastic” development.

But she cautioned: “We will still need other treatments too, we won’t replace them.”

Prof Jane Maher, chief medical officer at Macmillan Cancer Support, said: “The concept in principle is a really exciting one. But technologically there are real challenges in knowing how quickly this will happen.”

She said that tumours were often genetic mosaics and very good at developing resistance.

content aggregation:healthPrior21

source:telegraph.