Lung cancer screening

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Lung cancer screening is a strategy used to identify early lung cancer in people before they develop symptoms. 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 screening 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.

Regular chest radiography and sputum examination programs were not effective in reducing mortality from lung cancer.[1] Earlier studies (Mayo Lung Project and Czechoslovakia lung cancer screening study, combining over 17,000 smokers) showed earlier detection of lung cancer was possible but mortality was not improved. Simply detecting a tumor at an earlier stage may not necessarily yield improved mortality. For example, plain radiography 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, and it is showing promising results. The USA-based National Cancer Institute is currently completing a randomized trial comparing CT scans with chest radiographs. Several single-institution trials are ongoing around the world.

The International Early Lung Cancer Action Project is a cohort study 31,000 high-risk patients that found benefit from screening.[2] In this study 85% of the 484 detected lung cancers were stage I and thus highly treatable. Mathematically these stage I patients would have an expected 10-year survival of 88%. However, there was no randomization of patients (all received CT scans and there was no comparison group receiving only x-rays) and the patients were not actually followed out to 10 years post detection (the median followup was 40 months).

A cohort of 3,200 current or former smokers found no benefit. These patients 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.[3]

Subsequent randomized controlled trials have been performed or are in progress[4].

  • The National Lung Screening Trial (NLST) reported reduction advanced-stage cancers diagnosed.[5]
  • The DANTE trial has been inconclusive.[6]

References

  1. Manser RL, Irving LB, Stone C, Byrnes G, Abramson M, Campbell D (2004). "Screening for lung cancer". Cochrane database of systematic reviews (Online) (1): CD001991. DOI:10.1002/14651858.CD001991.pub2. PMID 14973979. Research Blogging.
  2. Henschke CI, Yankelevitz DF, Libby DM, Pasmantier MW, Smith JP, Miettinen OS (2006). "Survival of patients with stage I lung cancer detected on CT screening". N. Engl. J. Med. 355 (17): 1763-71. DOI:10.1056/NEJMoa060476. PMID 17065637. Research Blogging.
  3. Bach PB, Jett JR, Pastorino U, Tockman MS, Swensen SJ, Begg CB (2007). "Computed tomography screening and lung cancer outcomes". JAMA 297 (9): 953-61. DOI:10.1001/jama.297.9.953. PMID 17341709. Research Blogging.
  4. Gohagan JK, Marcus PM, Fagerstrom RM, et al (2005). "Final results of the Lung Screening Study, a randomized feasibility study of spiral CT versus chest X-ray screening for lung cancer". Lung Cancer 47 (1): 9-15. DOI:10.1016/j.lungcan.2004.06.007. PMID 15603850. Research Blogging.
  5. Aberle DR, DeMello S, Berg CD, Black WC, Brewer B, Church TR et al. (2013). "Results of the two incidence screenings in the National Lung Screening Trial.". N Engl J Med 369 (10): 920-31. DOI:10.1056/NEJMoa1208962. PMID 24004119. PMC PMC4307922. Research Blogging.
  6. Infante M, Cavuto S, Lutman FR, Passera E, Chiarenza M, Chiesa G et al. (2015). "Long-Term Follow-up Results of the DANTE Trial, a Randomized Study of Lung Cancer Screening with Spiral Computed Tomography.". Am J Respir Crit Care Med 191 (10): 1166-75. DOI:10.1164/rccm.201408-1475OC. PMID 25760561. Research Blogging.