Does screening reduce lung cancer mortality?
It’s not clear. Neither routine chest x-ray (with or without sputum cytology) nor low-dose computed tomography (CT) have been proven to reduce mortality when used for lung cancer screening, although low-dose CT screening does identify lung cancer at an early stage in high-risk patients (strength of recommendation: B, based on heterogeneous cohort studies). Large studies of both imaging approaches are ongoing.
Let’s prevent lung cancer so we don’t have to worry about screening
Tim Huber, MD
Oroville Hospital, Oroville, Calif
While some trials suggest possibly useful screening tools, and myriad other trials are underway, one point often gets short shrift: the importance of preventing cancer from occurring in the first place. Most family physicians already screen for smoking and offer counseling and pharmacologic assistance to smokers. We should also be aggressively counseling our adolescent and young adult patients against starting to smoke. Ideally, we would help people reduce their exposure to secondhand smoke, as well. When a teachable moment comes along, we should take the time to educate our patients about their specific risk factors and how they can be modified. Preventing the problem before it starts is our patients’ best defense against lung cancer.
Evidence summary
Chest x-ray and cytology: A trend toward reduced mortality
A Cochrane review1 identified 6 randomized controlled trials (RCTs) and 1 non-RCT (with a total of 245,610 patients) that screened patients with serial chest x-rays, with or without sputum cytology. Most patients were current or ex-smokers or had significant exposure to industrial smoke. No studies included an unscreened control group, and only 1 included women.
There was a trend toward reduced mortality with the combination of annual chest x-ray and sputum cytology compared with annual x-ray alone, but it was not statistically significant (relative risk [RR]=0.88; 95% confidence interval [CI], 0.74–1.03). However, more frequent screening with chest x-rays (2 or 3 times/ year) was associated with an 11% increase in mortality compared with less frequent x-rays (RR=1.11; 95% CI, 1.00–1.23). The authors concluded that there was insufficient evidence to support screening with chest x-ray or sputum cytology.
Low-dose CT: Studies reach different conclusions
A 2006 study followed a cohort of at-risk patients using low-dose CT screening.2 There were 31,567 patients evaluated initially, of which 27,456 had an annual repeat screening. Most patients were current or former smokers (83%); patients with exposure to occupational and secondhand smoke were also included. A positive initial screen was defined as a solid or partly solid noncalcified nodule ≥5 mm in diameter; a nonsolid, noncalcified nodule ≥8 mm in diameter; or a solid endobronchial nodule. A positive screen during follow-up was defined as any new noncalcified nodule, regardless of size.
Positive tests occurred in 13% of baseline screens and 5% of annual screens. Biopsies were performed according to a study protocol based on a nodule’s size and behavior over time. Out of a total of 5646 positive screens, there were 535 biopsies, and a diagnosis of cancer in 492 patients. Of those with cancer, 412 (84%) had clinical stage I lung cancer; the authors estimated their 10-year survival rate was 88% (95% CI, 84%–91%). If patients with stage I disease underwent surgical resection within 1 month of diagnosis, their estimated 10-year survival increased to 92% (95% CI, 88%–95%).
