Lung cancer screening

Lung cancer screening refers to strategies used to identify early lung cancers before they cause symptoms, at a point where they are more likely to be curable. Screening refers to the use of medical tests to detect disease in asymptomatic people. Screening studies have only been done in high risk populations, such as smokers and workers with occupational exposure to certain substances. This is because radiation exposure from repeated screening studies could actually induce cancer formation in a small percentage of screened subjects, so this risk should be mitigated by a (relatively) high prevalence of lung cancer in the population being screened.

Practice guidelines

Clinical practice guidelines issued by the American College of Chest Physicians in 2007 recommended against routine screening for lung cancer because of a lack of evidence that such screening was effective.cite journal |author=Alberts WM |title=Diagnosis and Management of Lung Cancer Executive Summary: ACCP Evidence-Based Clinical Practice Guidelines (2nd Edition) |journal= |volume=132 |issue=3_suppl |pages=1S–19S |year=2007 |pmid=17873156 |doi=10.1378/chest.07-1860]

In 2004, a clinical practice guideline by the US Preventive Services Task Force (USPSTF) gave a grade I recommendation indicating that "the evidence is insufficient to recommend for or against screening asymptomatic persons for lung cancer".cite journal |author=U.S. Preventive Services Task Force |title=Lung cancer screening: recommendation statement |journal=Ann. Intern. Med. |volume=140 |issue=9 |pages=738–9 |year=2004 |pmid=15126258 |doi=|url=http://www.annals.org/cgi/content/full/140/9/738] cite journal |author=Humphrey LL, Teutsch S, Johnson M |title=Lung cancer screening with sputum cytologic examination, chest radiography, and computed tomography: an update for the U.S. Preventive Services Task Force |journal=Ann. Intern. Med. |volume=140 |issue=9 |pages=740–53 |year=2004 |pmid=15126259 | url=http://www.annals.org/cgi/content/full/140/9/740 ]

tudies of efficacy

Regular chest radiography and sputum examination programs were not effective in reducing mortality from lung cancer.cite journal |author=Manser RL, Irving LB, Stone C, Byrnes G, Abramson M, Campbell D |title=Screening for lung cancer |journal=Cochrane database of systematic reviews (Online) |issue=1 |pages=CD001991 |year=2004 |pmid=14973979 |doi=10.1002/14651858.CD001991.pub2] Previous studies (Mayo Lung Project and Czechoslovakia lung cancer screening study, combining over 17,000 smokers) had shown that early detection of lung cancer was possible with such programs, but mortality was not improved. Simply detecting a tumor at an earlier stage may not necessarily lead to improved survival. For example, plain chest X-ray screening resulted in increased time from diagnosis of cancer until death and those cancers being detected by screening tended to be earlier stages. However, these patients continued to die at the same rate as those who are not screened. At present, no professional or specialty organization advocates screening for lung cancer outside of clinical trials.

A computed tomography (CT) scan can uncover tumors not yet visible on an X-ray. CT scanning is now being actively evaluated as a screening tool for lung cancer in high risk patients. The United States National Cancer Institute is currently completing a randomized trial comparing CT scans with chest radiograph, with results expected in 2010. Several other multi-institution trials are also ongoing around the world.

The International Early Lung Cancer Action Project (I-ELCAP) published the results of CT screening on over 31,000 high-risk patients in late 2006 in the "New England Journal of Medicine".cite journal |author=Henschke CI, Yankelevitz DF, Libby DM, Pasmantier MW, Smith JP, Miettinen OS |title=Survival of patients with stage I lung cancer detected on CT screening |journal=N. Engl. J. Med. |volume=355 |issue=17 |pages=1763–71 |year=2006 |pmid=17065637 |doi=10.1056/NEJMoa060476] In this study, 85% of the 484 detected lung cancers were stage I and thus highly treatable. Historically, such stage I patients would have an expected 10-year survival of 88%. Critics of the I-ELCAP study point out that there was no randomization of patients (all received CT scans and there was no comparison group receiving only chest x-rays) and the patients were not actually followed out to 10 years post detection (the median followup was 40 months). Regardless of these shortcomings, it is generally recognized that the prognosis of lung cancer decreases dramatically when the disease is in late stagecite journal |author=Mountain CF |title=Revisions in the International System for Staging Lung Cancer |journal=Chest |volume=111 |issue=6 |pages=1710–7 |year=1997 |month=June |pmid=9187198 |doi= |url=http://www.chestjournal.org/cgi/pmidlookup?view=long&pmid=9187198] cite journal |author=Inoue K, Sato M, Fujimura S, "et al" |title=Prognostic assessment of 1310 patients with non-small-cell lung cancer who underwent complete resection from 1980 to 1993 |journal=J. Thorac. Cardiovasc. Surg. |volume=116 |issue=3 |pages=407–11 |year=1998 |month=September |pmid=9731782 |url=http://linkinghub.elsevier.com/retrieve/pii/S0022-5223(98)70006-6] , and that CT screening for lung cancer allows detection of lung cancer during its earliest, most curable stage. CT screening for lung cancer has already been extensively compared to chest x-ray screening in Japan. Among over 6,800 subjects screened in Japan, 67% to 73% of CT-detected lung cancers were missed by chest x-ray, the same test used in the comparison group of some randomized controlled trials of lung cancer screening. cite journal |author=Kaneko M, Eguchi K, Ohmatsu H, "et al" |title=Peripheral lung cancer: screening and detection with low-dose spiral CT versus radiography |journal=Radiology |volume=201 |issue=3 |pages=798–802 |year=1996 |month=December |pmid=8939234 |doi= |url=http://radiology.rsnajnls.org/cgi/pmidlookup?view=long&pmid=8939234] cite journal |author=Sone S, Takashima S, Li F, "et al" |title=Mass screening for lung cancer with mobile spiral computed tomography scanner |journal=Lancet |volume=351 |issue=9111 |pages=1242–5 |year=1998 |month=April |pmid=9643744 |doi=10.1016/S0140-6736(97)08229-9 |url=] cite journal |author=Sone S, Li F, Yang ZG, "et al" |title=Results of three-year mass screening programme for lung cancer using mobile low-dose spiral computed tomography scanner |journal=Br. J. Cancer |volume=84 |issue=1 |pages=25–32 |year=2001 |month=January |pmid=11139308 |doi=10.1054/bjoc.2000.1531 |url=]

The ongoing trials for lung cancer screening have been shrouded in controversy. In October 8, 2007, the "Wall Street Journal" reported that at least two lead investigators of the National Lung Screening Trial (NLST), a federally-funded $200 million randomized lung cancer screening study, have conflicts of interest for serving as paid, expert defense witnesses for the tobacco industry. [http://online.wsj.com/article/SB119179920110451468.html?pagewanted=1&_r=1&hp Critics Question Objectivity Of Government Lung-Scan Study] , by David Armstrong. Published in the "Wall Street Journal" on October 8 2007] Additional controversy arose after a 2008 "New York Times" reported that the I-ELCAP had been funded indirectly by the parent company of the Liggett Group, a tobacco company. [http://www.nytimes.com/2008/03/26/health/research/26lung.html?pagewanted=1&_r=1&hp Cigarette Company Paid for Lung Cancer Study] , by Gardiner Harris. Published in the "New York Times" on March 26 2008.]

In contrast, a March 2007 study in the "Journal of the American Medical Association" (JAMA) found no mortality benefit from CT-based lung cancer screening.cite journal |author=Bach PB, Jett JR, Pastorino U, Tockman MS, Swensen SJ, Begg CB |title=Computed tomography screening and lung cancer outcomes |journal=JAMA |volume=297 |issue=9 |pages=953–61 |year=2007 |pmid=17341709 |doi=10.1001/jama.297.9.953] 3,200 current or former smokers were screened for 4 years and offered 3 or 4 CT scans. Lung cancer diagnoses were 3 times as high, and surgeries were 10 times as high, as predicted by a model, but there were no significant differences between observed and expected numbers of advanced cancers or deaths.cite journal |author=Crestanello JA, Allen MS, Jett J, Cassivi SD, et al. |title=Thoracic surgical operations in patients enrolled in a computed tomographic screening trial |journal=Journal of Thoracic and Cardiovascular Surgery |volume=128 |issue=2 |pages=254–259 |year=2004 |pmid=15282462 |doi=10.1016/j.jtcvs.2004.02.017]

Randomized controlled studies are underway in this area to see if decreased long-term mortality can be directly observed from CT screening.cite journal |author=Gohagan JK, Marcus PM, Fagerstrom RM, "et al" |title=Final results of the Lung Screening Study, a randomized feasibility study of spiral CT versus chest X-ray screening for lung cancer |journal=Lung Cancer |volume=47 |issue=1 |pages=9–15 |year=2005 |pmid=15603850 |doi=10.1016/j.lungcan.2004.06.007]

References