Other causes include radon, exposure to secondhand smoke, exposure to substances such as asbestos, chromium, nickel, beryllium, soot, or tar, family history of lung cancer, and air pollution.Genetics can also play a role as a family history of lung cancer can contribute to an increased risk of developing the disease. Furthermore, research has revealed specific chromosome regions associated with increased risks of developing lung cancer. In general, DNA damage appears to be the primary underlying cause of cancer. Though most DNA damages are repairable, leftover unrepaired DNA damages from cigarette smoke are the likely cause of NSCLC. DNA replication past an unrepaired damage can give rise to a mutation because of inaccurate translesion synthesis. In addition, during repair of DNA double-strand breaks, or repair of other DNA damages, incompletely cleared sites of repair can lead to epigenetic gene silencing. DNA repair deficiency in NSCLC
Deficiencies in DNA repair underlie many forms of cancer. If DNA repair is deficient, the frequency of unrepaired DNA damages increases, and these tend to cause inaccurate translesion synthesis leading to mutation. Furthermore, increased damages can elevate incomplete repair, leading to epigenetic alterations.As indicated as in the article Carcinogenesis, mutations in DNA repair genes occasionally occur in cancer, but deficiencies of DNA repair due to epigenetic alterations that reduce or silence DNA repair-gene expression occur much more frequently in cancer.Epigenetic gene silencing of DNA repair genes occurs frequently in NSCLC. At least nine DNA repair genes that normally function in relatively accurate DNA repair pathways are often repressed by promoter hypermethylation in NSCLC.
Five-year survival rates
The survival rates for stages I through IV decrease significantly due to the advancement of the disease. For stage I, the five-year survival rate is 47%, stage II is 30%, stage III is 10%, and stage IV is 1%. Treatment
More than one kind of treatment is often used, depending on the stage of the cancer, the individuals overall health, age, response to chemotherapy, and other factors such as the likely side effects of the treatment. After full staging, the NSCLC patient can typically be classified in one of three different categories: patients with early, nonmetastatic disease (stages I and II, and select type III tumors), patients with locally advanced disease confined to the thoracic cavity (e.g., large tumors, tumors involving critical chest structures, or patients with positive mediastinal lymph nodes), or patients with distant metastasis outside of the thoracic cavity. Early/nonmetastatic NSCLC
NSCLCs are usually not very sensitive to chemotherapy and/or radiation, so surgery (lung resection to remove the tumor) remains the treatment of choice if patients are diagnosed at an early stage.If the persons have a small, but inoperable tumor, they may undergo highly targeted, high-intensity radiation therapy. New methods of giving radiation treatment allow doctors to be more accurate in treating lung cancers. This means less radiation affects nearby healthy tissues. New methods include Cyberknife and stereotactic body radiation therapy. Certain people who are deemed to be higher risk may also receive adjuvant (ancillary) chemotherapy after initial surgery or radiation therapy.