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lung cancer screening - NOT GOOD NEWS


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The Cochrane Database is compiled by a group of researchers who meta-analyze health studies (that is, they statistically combine many different trials to form reliable conclusions.) Their conclusions are widely respected. Note that this meta-analysis did not include any studies of CT screening, which is currently being evaluated in the Lung Screening Trial.




Manser, RL; Irving, LB; Stone, C; Byrnes, G; Abramson, M; Campbell, D


Screening for lung cancer.


Cochrane Database of Systematic Reviews. 1, 2005.



While population based screening for lung cancer has not been adopted by most countries, it is not clear whether sputum examinations, chest radiography or newer methods such as computed tomography are effective in reducing mortality from lung cancer.


To determine whether screening for lung cancer using regular sputum examinations or chest radiography or CT chest reduces lung cancer mortality.

Search strategy:

Electronic databases (the Cochrane Central Register of Controlled Trials, MEDLINE, PREMEDLINE and EMBASE; 1966 to July 2000)), bibliographies, hand searching of a journal and discussion with experts were used to identify published and unpublished trials.

Selection criteria:

Controlled trials of screening for lung cancer using sputum examinations, chest radiography or CT chest.

Data collection and analysis:

Intention to screen analysis was performed. Where there was significant statistical heterogeneity relative risks were reported using the random effects model, but for other outcomes the fixed effect model was used.

Main results:

Seven trials were included (6 randomised controlled studies and 1 non-randomised controlled trial) with a total of 245,610 subjects. There were no studies with an unscreened control group. Frequent screening with chest x-rays was associated with an 11% relative increase in mortality from lung cancer compared with less frequent screening (RR 1.11, CI: 1.00-1.23). A non statistically significant trend was observed to reduced mortality from lung cancer when screening with chest x-ray and sputum cytology was compared with chest x-ray alone (RR 0.88, CI:0.74-1.03). Several of the included studies had potential methodological weaknesses. There were no controlled studies of spiral CT.


The current evidence does not support screening for lung cancer with chest radiography or sputum cytology. Frequent chest x-ray screening might be harmful. Further, methodologically rigorous trials are required.


Please note that the fact that chest x-ray screening "might be harmful" does not necessarily mean that the x-ray itself is harmful. It may mean that benign tumors were detected more often, and therefore patients were subjected to diagnostic procedures that carried risk, such as invasive biopsies. The article says, "The results of this review should be interpreted with caution. We identified potentially important methodological weaknesses in most of the studies included in the review."

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I haven't read the full article but I did have a thought when reading this section of the conclusion:

"Frequent screening with chest x-rays was associated with an 11% relative increase in mortality from lung cancer compared with less frequent screening" (RR 1.11, CI: 1.00-1.23

Is it a possiblity that the increase in mortality seen with frequent x-rays is a reflection that patients with more advanced disease have more frequent x-rays. And as patients with more advanced disease have an increased mortality, perhaps this statistics are a reflection of this. I wonder if the study controlled for stage of disease as a confounding factor????




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