Unequal access to a vital blood test means thousands of cancer patients may not be receiving the best treatment, a study has shown.
Some could be having their life shortened by receiving the wrong targeted drug, research suggests.
The free genetic test helps doctors determine what drugs will be most effective for individual patients with bowel cancer.
But newly diagnosed patients are much more likely to be offered the test in some parts of the UK than in others, scientists found.
The study revealed “significant disparities” across the UK. Patients living in London, south-east England and the Midlands stood a much greater chance of being tested than those from Yorkshire, Humberside and the North East.
Other findings from a cancer conference this week confirmed that the test for different versions of the KRAS gene can affect life-or-death treatment decisions.
Each year more than 40,000 people in the UK are diagnosed with bowel cancer, over half with advanced and spreading disease.
The disease is Britain’s second biggest cancer killer after lung cancer, claiming around 16,000 lives a year.
Dr Harpreet Wasan, from Imperial College London, who led the team investigating the diagnostic lottery, said: “KRAS biomarker testing should invariably be performed in all bowel cancer patients at diagnosis, in order to ensure that clinicians can make the most informed treatment decisions, particularly for those with the most advanced forms of the disease.
“The KRAS variations data shows a big difference in the rates of free KRAS testing. Therefore, some patients who are not being tested for KRAS could be missing out on the best possible treatment approaches available to them.”
KRAS testing at 21 centres across the UK is currently funded by the drug company Merck Serono and offered freely to all NHS patients diagnosed with bowel cancer.
Guidelines from the European Society for Medical Oncology recommend the test for all patients with advanced disease.
In England, the National Institute for health and Clinical Excellence (NICE), is in the process of developing its own KRAS test guidance.
Around 45% of patients have a mutated version of the KRAS gene, while the rest have a “wild-type” or unmutated variant.
Research shows that the drug Avastin is most effective for patients with the mutated gene. Patients with the unmutated gene respond less well to Avastin and better to another drug, Erbitux.
However, since Erbitux is highly ineffective in patients with mutated KRAS genes, Avastin tends to be more widely prescribed. Both drugs cost about the same, £10,000 - £15,000 per year.
The KRAS test study was based on Strategic Health Authority regions. It showed that between 2012 and 2013, just over 6% of patients in Yorkshire and Humber were tested compared with around 48% in the South East Coast, 40.5% in the South Central, and 32% in the London regions.
In Scotland, 13% of patients were tested, in Wales 18%, and in the South West and North East regions 6%.
Northern Ireland had far and away the greatest access to KRAS testing, with a take-up rate of more than 70%.
A summary of the findings presented at the European Society for Medical Oncology (Esmo) meeting in Barcelona, Spain, concluded: “This analysis shows that significant disparities in KRAS mutational status testing exist between SHAs and Cancer Networks across the UK, despite equal access to free testing.”
Are you able to Speak Out Safely? Sign our petition to put pressure on your trust to support an open and transparent NHS.