Doctors on Wednesday said they had used a wide-ranging genetic test for mutations in cancer cells to help finetune treatment for patients with lung tumours. Used on patients with so-called non-small-cell lung cancer (NSCLC), the technique has been such a success that the team is now using it for colorectal, breast and brain cancer and are assessing it for leukaemia, they said. The goal is to identify specific genetic mutations that enable cells to divide and multiply unchecked. The next step is to target these mutations with "smart drugs" that block the enzyme which enables the cells to proliferate. Tailored drugs are considered like a sniper's rifle, seeking out the type of rogue cell, as opposed to chemotherapy, which acts more like a scattergun. "Choosing the right therapy can raise response rates [to drugs] in NSCLC patients from around 20-30 percent to 60-75 percent and may improve surival," said Lecia Sequist of Harvard Medical School and Massachusetts General Hospital, who co-led the research. The test, called SNaPshot, looks for 50 mutation sites in 14 genes known to play a role in NSCLC. By fast-tracking traditional methods for amplifying and analysing gene samples, called polymerase chain reaction (PCR), the technique takes less than three weeks on average to get the results. The investigators analysed tissue taken from 589 patients in a 14-month trial and found one or more mutations in just over half of the samples. Out of the 589 patients, there were 353 with advanced cancer. And in 170 of these, the doctors were able to pinpoint one or more genes that were troublemakers. That discovery opened the way to having 78 patients gain targeted therapy. Sequest said this is the first time that such a wide net of faulty genes has been cast to create a genotype -- or genetic profile -- for use in cancer treatment. "Our study is exciting because it demonstrates that indeed it is possible today to integrate testing for multiple genetic biomarkers into a busy clinic and steer patients toward personalised therapies," she said in a press release. Genotyping is a fast-developing tool in preventive medicine, helping doctors to identify, for instance, women at risk of breast cancer. The trial is written up in a European cancer journal, Annals of Oncology.