CT screening proven effective for lung cancer

By Joanna Lyford, Senior medwireNews Reporter

There is strong evidence to support the effectiveness of screening for lung cancer with low-dose computed tomography (LDCT), a systematic review has found.

This conclusion was driven by results of a large US trial in which LDCT screening of high-risk individuals aged 55–74 years reduced both lung cancer-specific and all-cause mortality when compared with annual chest radiography.

The number needed to screen (NNS) to prevent one death from lung cancer was 320 over 6.5 years, the authors calculated, which compares favorably with the NNS for other screening strategies.

“The personal and public health consequences of lung cancer are enormous, and even a small benefit from screening could save many lives,” remark Linda Humphrey (Oregon Health & Science University, Portland, USA) and co-authors of the review, which is published in the Annals of Internal Medicine.

The review was an update of the 2004 report by the US Preventive Services Task Force, which judged the evidence about the effectiveness of lung cancer screening with chest radiography or LDCT to be insufficient.

From a literature search, Humphrey’s group identified four trials that reported results of LDCT screening in current or former smokers. These were the National Lung Screening Trial (NLST), the Detection and Screening of Early Lung Cancer by Novel Imaging Technology and Molecular Essays trial, the Danish Lung Cancer Screening Trial , and Multicentric Italian Lung Detection trial.

Just one study, the NLST, was judged to be of good quality. In this trial, nearly 27,000 patients were screened with LDCT at 0, 1, and 2 years and followed up for a median of 6.5 years. Compared with chest radiography, LDCT reduced lung cancer mortality by 20% and all-cause mortality by 6.7%.

The investigators calculated that the NNS among people who underwent at least one LDCT screening was 320 for lung cancer mortality and 219 for all-cause mortality.

The other three trials, which were small and judged to be of fair or poor quality, found no benefit from LDCT screening as compared with usual care or no lung cancer screening.

Humphrey et al note that a quarter of deaths in the control group of the NLST were from lung cancer, a figure that highlights “the large contribution of this disease to overall mortality in this age and risk strata of this population.”

While concluding that LDCT “seemed to reduce lung cancer mortality,” the authors note that screening is also associated with risks, such as false reassurance, false–positive findings, overdiagnosis, and psychosocial consequences.

“[I]dentifying and treating early-stage lung cancer with screening will hopefully clarify the balance of benefits and harms associated with screening,” they note.

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