Causes Of Lung Cancer - large cell carcinoma of lung

Smoking, large cell carcinoma of lung particularly of cigarettes, is believed to be by far the main cause of cancer, which in at least in theory makes it one of the easiest diseases to prevent. An estimated 80% of lung cancers result from smoking, due to the hundreds of known carcinogens, such as benzene, present in cigarette smoke. The length of time that a person continues to smoke as well as the amount smoked increases there chances of contracting lung cancer. However if someone stops smoking then these chances steadily decrease as the damage to their lungs is repaired.

Passive smoking, whereby exhaled smoke is taken up by other people, has recently been identified as a much larger cause of lung cancer in non-smokers than previously believed. The US Environmental Protection Agency (EPA) in 1993 concluded that about 3,000 lung-cancer related deaths were caused by passive smoking every year, however the true extent is still being contested among scientists.

Radon is a colourless and odorless gas derived from the breakdown of radioactive radium, which in turn is the decayed product of uranium, found in the earth's crust. It is the second major cause of lung cancer after smoking. This radiation ionises genetic material, causing mutations that sometimes become cancerous. Radon gas levels vary over where you live. In areas such as Cornwall in the UK, radon-gas is a major problem, and fans have to be installed to drive out the gas. In the US the EPA estimated that 1 in 15 homes have radon levels above the recommended standard.

Oncogenes are genes which is believed make people more susceptible to cancer. Proto-oncogenes are believed to turn in to oncogenes when exposed to particular carcinogens. Viruses are suspected to cause cancer in humans, as this link has already been proven in animals.

Prevention Of Lung Cancer

Prevention plans are the most cost-effective means of fighting lung cancer on national and global scale. While in most countries industrial and domestic carcinogens have been identified and banned, tobacco smoking still is quite widespread. Fighting tobacco smoking should be primary goal for lung cancer prevention.

Because prognosis depends heavily on early detection there have been several attempts at secondary prevention. Regular chest radiography and sputum examination programs were not effective in early detection of this cancer and did not resulted in reduction of mortality. However in September 2003 one study published in Lancet is quite promising. The study showed that spiral computed tomography and positron emission tomography were effective in detecting early stages of lung cancer in high risk population of heavy smokers.

Small Cell Lung Cancer Treatment

Without treatment, small cell lung cancer (SCLC) has the most aggressiveclinical course of any type of pulmonary tumor, with median survival fromdiagnosis of only 2 to 4 months. Compared with other cell types of lungcancer, SCLC has a greater tendency to be widely disseminatedby the time of diagnosis but is much more responsive to chemotherapy andradiation therapy.

Because patients with small cell lung cancer tend to develop distantmetastases, localized forms of treatment, such as surgical resection orradiation therapy, rarely produce long-term survival.[2] With incorporation ofcurrent chemotherapy regimens into the treatment program, however, survival isunequivocally prolonged, with at least a 4- to 5-fold improvement in mediansurvival compared with patients who are given no therapy. Furthermore, about10% of the total population of patients remains free of disease during 2 yearsfrom the start of therapy, the time period during which most relapses occur. Even these patients, however, are at risk of dying from lung cancer (both small-and non-small cell types).[3] The overall survival at 5 years is 5% to10%.[3][4][5]

At the time of diagnosis, approximately 30% of patients with SCLC will have tumor confined to the hemithorax of origin, themediastinum, or the supraclavicular lymph nodes. These patients are designatedas having limited-stage disease, and most 2-year disease-free survivors comefrom this group. In limited-stage disease, median survival of 16 to 24 monthswith current forms of treatment can reasonably be expected.[6][7][8] A smallproportion of patients with limited-stage disease may benefit from surgery withor without adjuvant chemotherapy; these patients have an even better prognosis.

Patients with tumors that have spread beyond the supraclavicular areas are saidto have extensive-stage disease and have a worse prognosis than patients withlimited-stage disease. Median survival of 6 to 12 months is reported with currentlyavailable therapy, but long-term disease-free survival is rare.

The pretreatment prognostic factors that consistently predict for prolongedsurvival include good performance status, female gender, and limited-stagedisease.[4][9][10] Patients with involvement of the central nervous system orliver at the time of diagnosis have a significantly worse outcome.[4][9][10][11] Ingeneral, patients who are confined to bed tolerate aggressive forms oftreatment poorly, have increased morbidity, and rarely attain 2-yeardisease-free survival; however, patients with poor performance status canoften derive significant palliative benefit and prolongation of survival fromtreatment.

Regardless of stage, the current prognosis for patients with SCLC is unsatisfactory even though considerable improvements in diagnosis andtherapy have been made during the past 10 to 15 years. All patientswith this type of cancer may appropriately be considered for inclusion inclinical trials at the time of diagnosis. Information about ongoing clinical trials is available from theNCI Web site.

Recurrent Small Cell Lung Cancer

Note: Some citations in the text of this section are followed by a level ofevidence. The PDQ editorial boards use a formal ranking system to help thereader judge the strength of evidence linked to the reported results of atherapeutic strategy. (Refer to the PDQ summary on Levels of Evidence for moreinformation.)

Some patients with intrinsic endobronchial obstructing lesions or extrinsiccompression caused by tumor have achieved successful palliation with endobronchiallaser therapy (for endobronchial lesions only) and/or brachytherapy.[10] Expandable metal stents can be safely inserted under local anesthesia via thebronchoscope, which results in improved symptoms and pulmonary function in patientswith malignant airways obstruction.[11] Patients with progressiveintrathoracic tumor after failing initial chemotherapy can achieve significantexternal-beam radiation therapy. Only the rare patient, however, willexperience long-term survival following salvage radiation therapy.[12]

Patients with central nervous system recurrences can often obtain palliation ofsymptoms with radiation therapy and/or additional chemotherapy. The majorityimprovement following radiation therapy.[13] A retrospective review showedthat 43% of patients treated with additional chemotherapy at the time of central nervous system relapse respond to second-line chemotherapy.[14]