Using CT scans to screen heavy smokers or ex-smokers can reduce lung cancer deaths by 20 per cent, according to a large study from the US National Cancer Institute. At first glance, the research is good news in the fight against lung cancer. Yet the results are being overstated by companies who produce the scanners, ignoring the potential risks of widespread use of the test.

The US National Lung Screening Trial started in 2002 and involved 53,000 people aged 55 to 74 who had at least a 30 pack year history of smoking cigarettes. This means that they had either smoked three packs a day for 10 years or one pack a day for 30 years. The sample group therefore had a high risk of developing lung cancers. The research analysed the risk of dying from lung cancer when using either the new 3-D scan or the conventional chest X-rays.

The use of spiral CT scans has increased dramatically over the last two decades. A CT lung scan is different from standard X-rays. It uses thousands of two-dimensional X-ray images to generate a three-dimensional image of lung tissue. It therefore gives clinicians a multiple-image scan of the entire chest allowing them to find even the smallest tumours. However, the scans use an extremely high dose of radiation to generate the images, which actually increases the chance of getting a lung cancer.

Those who participated in the trial were screened for lung cancer using either a single frontal chest X-ray or a CT scan every year for three years. The patients were then monitored for up to five years and lung cancer death rates in both groups recorded; a 20 per cent reduction for the CT scan group.

Those undergoing too many lung cancer scans ‘could develop breast cancer’

The research is good news for the detection of lung cancer, but one should not forget the risks associated with high resolution CT scans. Professor Stephen Duffy, screening expert at Cancer Research UK, believes the results of the study are “very encouraging” but a full analysis is needed to confirm these risks.

While CT scans are painless they expose patients to radiation that can potentially cause new cancers. Ned Patz, professor of radiology at Duke University Medical Center who helped design the trial, said that a person receiving frequent CT scans in order to detect lung cancer could develop breast cancer or other lung cancers as a result of the tests.

It is also important to be aware that screenings do not diagnose cancer. They only detect potential problems that must then be analysed further by doctors in order to confirm or deny the presence of cancer, using tissue analysis. Tissue is retrieved by making an incision through the ribs to perform a lung biopsy, a serious and risky operation.

Moreover, screenings often detect suspicious lumps and bumps that turn out to be benign tumours. Increased use of CT scans would inevitably lead to invasive investigation of far more benign nodules, causing unnecessary worry and pain to many patients and carrying huge financial implications for healthcare providers.

Should everyone be screened for lung cancer?

‘No’ is the common answer among experts who reacted after the results of the study were published.

Lung cancer is the leading cause of cancer mortality worldwide, according to the World Health Organisation. Although there are 100 million smokers and ex-smokers in the USA, many lung cancer cases are diagnosed in people who have either quit smoking or never used tobacco. This news may be reassuring for many worried ex-smokers. However, doctors believe that this information could spur more non-smokers to ask for the scans.

The fact is that researchers cannot tell whether CT screening programmes help non-smokers or people younger than 55. Chief Medical Officer of the American Cancer Society stated that for now “no medical groups should endorse screening for lung cancer”. Dr Otis Brawley advised people to “have conversations with their doctors about whether lung cancer screening is right for them”.

He also warned that the benefits of screening in the real world may not be the same as in the study. For instance, whilst heavy smokers and ex-smokers participating in the trial lived in large cities and were treated at major cancer centres, many people are screened at community hospitals. Smaller facilities tend to have less technologically advanced follow-up procedures for suspicious results, meaning CT scans for all patients may simply be impossible.

Finally, what the study shows is only applicable to a specific group of people: heavy smokers. Deputy Chief Medical Officer for the American Cancer Society, Dr Leonard Lichtenfeld, said that it does not give any useful information to non-smokers, ex-smokers or people who only smoke lightly – and still develop lung cancer. He stated: “If you are a younger person, who has ‘only’ smoked a pack a day for 20 years, this study tells you nothing”.

The rise of an against-lung cancer business

Since the study was published, increased marketing of CT scans has started. For example, Minnesota Lung Center, specialists in pulmonary disease diagnostics, has published advertisements for lung cancer screenings that mention the study in support of their services: “Minnesota Lung Center is now offering lung cancer screening. Please contact our centralised call centre to schedule an appointment”.

Health care journalist Gary Schwitzer has strongly criticised the advertisement, saying: “Nowhere in the ad will you read about the potential harms of such scans; the false positive rate, what happens when you get a false positive and more costs”. The advert also fails to mention that 300 heavy smokers had to be scanned in order for just one to benefit from the screening and extend their life. “But six clinics in this chain are standing by to take your money and do your scan”, Schwitzer added.

Currently, neither Medicare (a social insurance programme administered by the government of the United States), nor private insurance companies pay for lung cancer screenings with CT scans, according to the director of the US National Cancer Institute Harold Varmus. However, insurance plans generally do pay for diagnostic CT scans when patients already have other signs of lung cancer.

In the battle against breast cancer, health officials can now provide mammograms for less than US$100, enabling access to large numbers of younger and poorer women to receive screening. Harold Varmus said that the Medicare programme plans to review the study results to decide whether to cover lung screenings for high-risk patients. In the meantime, it is unclear at what age screening for lung cancer should begin, how often screening should occur or even who is at high-risk.

As companies continue to spin the results in an attempt to increase profits, the true implications of the research remain unclear. Yet all health advisors are clear on one thing: smoking is still highly linked to lung cancer. So, in order to reduce the risk of getting the disease, you may want to quit – or better still never start.