CT screening fails to improve lung cancer mortality
MedWire News: Study findings suggest that low-dose computed tomography (CT) screening improves detection of early-stage lung cancer but without an associated disease stage shift or reduction in mortality.
"A high frequency of early stage cancers is only beneficial if at the same time the frequency of late stage cancers is reduced, implying a reduction in mortality," say Zaigham Saghir (Gentofte University Hospital, Hellerup, Denmark) and colleagues.
In addition, overdiagnosis can be harmful because it may imply unnecessary investigations and treatment.
Within the Danish Lung Cancer Screening Trial (DLCST), 4104 individuals who were healthy heavy smokers or former smokers were randomly assigned to receive five annual low-dose CT screenings or no screening.
Nodules that were 1-15 mm in size without benign characteristics were rescanned after 3 months, while growing nodules (>25% volume increase and/or volume doubling time <400 days) and nodules larger than 15 mm were referred for diagnostic workup. In the control group, lung cancers were diagnosed and treated outside the study according to usual clinical practice.
Saghir and colleagues found that the average detection rate of 0.67% observed during screening rounds 1 to 4 was similar to the baseline round lung cancer detection rate of 0.83%.
Furthermore, significantly more lung cancers were diagnosed in the screening group compared with controls (69 vs 24 cancers). A greater proportion of these cancers were at a low stage among patients in the screening group (48 vs 21 stage I-IIB non-small cell lung cancers [NSCLC] and limited SCLC), whereas frequencies of high-stage lung cancer were the same (21 vs 16 stage IIIA-IV NSCLC and extensive stage SCLC).
The researchers say this finding "may indicate a considerable degree of overdiagnosis or a longer lead time until clinical diagnosis in the control group is made and registered."
No significant reduction in mortality was observed for the screening group compared with controls (61 vs 42 patients), with 15 and 11 patients dying from lung cancer, respectively.
Writing in Thorax, the team concludes: "With screening, low-stage lung cancers are diagnosed more frequently but at this point no stage shift is observed and pooling of mortality data with European screening trials is needed."
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By Ingrid Grasmo