Misplaced Pages

Revision as of 22:51, 7 May 2007

Lung cancer
Specialty	Oncology, pulmonology

Lung cancer is the malignant transformation and expansion of lung tissue, and is the most lethal of all cancers worldwide, responsible for 1.2 million deaths annually. It is caused predominantly by cigarette smoking, and predominantly affects men, with it being the leading cause of death of men between the ages of 40 and 65. With increased smoking among women, it is now occuring in women but it is less common. While some people who have never smoked do still get lung cancer, this appears to be due to a combination of genetic factors and exposure to secondhand smoke.

Current research indicates that the factor with the greatest impact on risk of lung cancer is long-term exposure to inhaled carcinogens. The most common means of such exposure is air pollution and tobacco smoke.

Treatment and prognosis depend upon the histological type of cancer, the stage (degree of spread), and the patient's performance status. Treatments include surgery, chemotherapy, and radiotherapy.

Lung cancer staging

Lung cancer staging is an important part of the assessment of prognosis and potential treatment for lung cancer.

See non-small cell lung cancer staging.

Epidemiology

The population segment most likely to develop lung cancer is the over-fifties who also have a history of smoking. Lung cancer is the second most commonly occurring form of cancer in most western countries, and it is the leading cancer-related cause of death for men and women. In the US, 175,000 new cases are expected in 2006: 90,700 in men and 80,000 in women. Although the rate of men dying from lung cancer is declining in western countries, it is actually increasing for women due to the increased takeup of smoking by this group. Among lifetime non-smokers, men who have never smoked have higher age-standardized lung cancer death rates than women. Of the 80,000 women who are diagnosed with lung cancer in 2006, approximately 70,000 are expected to die from it.

Lung cancer was extremely rare prior to the advent of cigarette smoking. In 1878, malignant lung tumors made up only 1% of all cancers seen at autopsy; this had risen to 10-15% by the early 1900s. Case reports in the medical literature numbered only 374 worldwide in 1912. The British Doctors Study, published in the 1950s, first offered solid epidemiological evidence on the link between lung cancer and smoking.

Not all cases of lung cancer are due to smoking, but the role of passive smoking is increasingly being recognized as a risk factor for lung cancer, leading to policy interventions to decrease undesired exposure of non-smokers to others' tobacco smoke. Emissions from automobiles, factories and power plants also pose potential risks.

In the Second World and Third World, smoking-related lung cancer is rising rapidly in incidence. Countries such as China are expected to see a marked increase in lung cancer cases as smoking is exceedingly common and other causes of death (such as infections) are becoming less common, revealing an "iceberg" of pulmonary neoplasms. Cheap tobacco products and heavy advertising are seen by health campaigners as a major problem in these countries.

Prevention

Primary prevention

Prevention is the most cost-effective means of fighting lung cancer on the national and global scales. While in most countries industrial and domestic carcinogens have been identified and banned, tobacco smoking is still widespread. Eliminating tobacco smoking is a primary goal in the fight to prevent lung cancer, and smoking cessation is the most important preventative tool in this process.

Policy interventions to decrease passive smoking (e.g. in restaurants and workplaces) have become more common in various Western countries, with California taking a lead in banning smoking in public establishments in 1998, Ireland playing a similar role in Europe in 2004, followed by Italy and Norway in 2005 and Scotland as well as several others in 2006. New Zealand has also recently banned smoking in public places. (See Smoking ban).

Only the Asian state of Bhutan has a complete smoking ban (since 2005). In many countries pressure groups are campaigning for similar bans. Arguments cited against such bans is criminalisation of smoking, increased risk of smuggling and the risk that such a ban cannot be enforced.

Screening and secondary prevention

Regular chest radiography and sputum examination programs were not effective in reducing mortality from lung cancer. 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 published the results of CT screening on over 31,000 high-risk patients in late 2006 in the New England Journal of Medicine. 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).

In contrast, a March 2007 study in JAMA found no benefit. 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.

Randomized controlled studies are underway in this area to see if decreased long-term mortality can be directly observed from CT screening.

It should be noted that screening studies have only been done in high risk populations, such as smokers and workers with occupational exposure to certain substances. This is important when one considers that repeated radiation exposure from screening could actually induce carcinogenesis 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.

References

1. National Lung Cancer Partnership: Lung Cancer in American Women
2. Gorlova OY, Weng SF, Zhang Y, Amos CI, Spitz MR. Aggregation of cancer among relatives of never-smoking lung cancer patients. Int J Cancer. 2007 Feb 15;121(1):2865-2872 PMID 17304511
3. Sasco AJ, Secretan MB, Straif K. Tobacco smoking and cancer: a brief review of recent epidemiological evidence. Lung Cancer. 2004 Aug;45 Suppl 2:S3-9. PMID 15552776
4. Hackshaw AK, Law MR, Wald NJ. The accumulated evidence on lung cancer and environmental tobacco smoke. BMJ. 1997 Oct 18;315(7114):980-8. PMID 9365295
5. Lung Cancer in the United States: Facts from National Lung Cancer Partnership new cases of lung cancer in the US
6. New survey finds most women don't know much about lung cancer even though it's the leading cancer killer of women in the U.S from National Lung Cancer Partnership News
7. Witschi H. A short history of lung cancer. Toxicol Sci. 2001 Nov;64(1):4-6. PMID 11606795
8. Adler I. Primary malignant growths of the lungs and bronchi. New York: Longmans, Green, and Company; 1912., cited in Spiro SG, Silvestri GA. One hundred years of lung cancer. Am J Respir Crit Care Med. 2005 Sep 1;172(5):523-9. PMID 15961694
9. Screening for lung cancer, The Cochrane Database of Systematic Reviews 2007
10. Henschke CI, et al, Survival of patients with stage I lung cancer detected on CT screening. N Engl J Med. 2006 Oct 26;355(17):1763-71. PMID 17065637
11. Peter B. Bach, et al., Computed Tomography Screening and Lung Cancer Outcomes, JAMA. 2007;297:953-961. (March 7, 2007)

External links

• Informative video about Lung Cancer
• Lung Cancer Resources Page at the National Cancer Institute.
• Tobacco Smoke and Involuntary Smoking, Summary of Data Reported and Evaluation 2004 by the IARC.
• Lung Cancer Articles & Information Stop Smoking Articles & Information
• RadiologyInfo - The radiology information resource for patients with lung cancer

• Pulmonology
• Types of cancer