How to detect the deadliest form of cancer

Lung cancer is the deadliest of cancers. Screening could save thousands of lives, so why is it not the norm?

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Lung cancer kills more people than any other form of tumour.
About nine out of ten people die within five years of being diagnosed with the disease. If the cancer is caught very early most patients could be cured. But doctors struggle to diagnose early because there are no symptoms until the cancer is in its late stages and has spread to other organs.

Some experts think that doctors should screen people at high risk to find lung cancer before symptoms appear. The national lung-screening trial in America subjected 53,000 current and former heavy smokers to either X-ray or computed-tomography scans every year for three years. Its results, reported in 2011 found that screening with CT scans did save lives.

But there was a problem. Too many of the lumps found during the screening were not cancer. This is known as a false positive. False positives can harm patients who undergo dangerous follow-up procedures such as biopsies, even if they do not have cancer.

It can also affect their mental health and false positives add to the cost of health care. According to new data from the World Health Organisation these harms can be greatly reduced by following a different protocol. Instead of treating all lumps as a positive result doctors are now advised to ignore the smallest nodules and treat them as a negative result. This has halved the rate of false positives.

Out of every 1,000 people who were scanned 356 people required follow-up testing under the old protocol. With the new protocol, that has fallen to 180.

Complications from follow-up testing have also been reduced. These results show promise. Many countries are waiting for the full report of another trial called Nelson before deciding whether to set up fully fledged screening programmes. Preliminary data from the Nelson trial suggest that screening reduces the death rate from lung cancer among high-risk men by 26% and 61% in women.

If a balance between the cost and benefits of screening can be found, lung cancer need no longer be a death sentence.

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