As with most cancers, lung cancer is classified into various subtypes. The major divisions are small cell (approximately 15 percent of lung cancers) and non-small cell (all others). The small cell type is more aggressive, has a shorter life expectancy, and is more closely associated with cigarette smoking. Approximately 95 percent of these cases are attributed to smoking. Women who start smoking at an early age are the most susceptible.
Several genetic factors are associated with small cell lung cancer. I often hear smokers make comments denying the link between smoking and cancer, such as “Grandpa smoked all his life and never got cancer” or “Chuck got lung cancer but never smoked.” I think it's important to realize that a strong correlation does not mean 100 percent. If we could eliminate 95 percent of the lung cancers that lie in the future for our family and friends, that would be a huge improvement.
Small cell lung cancer is further classified as limited-stage disease or extensive disease. Historical data indicate that without treatment, the median survival time is only 12 weeks for limited-stage disease, and six weeks for extensive disease. Approximately 70 percent of patients have extensive disease by the time they're diagnosed. Symptoms include cough, shortness of breath, wheezing, and chest pain. Coughing up blood is one that often sends patients to a doctor for diagnosis. Small cell lung cancer metastasizes easily, and is therefore considered a systemic disease. Common sites of metastasis include bone, liver, lymph nodes, central nervous system, and adrenal glands. Symptoms of pain, headache, malaise (flu-like feeling), seizures, fatigue, loss of appetite, and weight loss are characteristic of metastatic disease.
Patients with limited-stage disease often respond well to chemotherapy, and surgery is an option for a few cases. Unfortunately, treatment options for extensive disease are not very encouraging. Chemotherapy can extend median survival time from six weeks to about 10 months. A recent review article analyzed median survival time versus year of clinical trial for 52 trials over a 27-year period (1981 to 2008). The improvement, averaged over all trials, is only 17 days. These trials studied 110 different chemotherapy options.
Clearly, we need research on a different approach to treating small cell lung cancer. Until we learn more about it, the only reasonable defense is smoking cessation.
References:
1. Sher T et al, “Small cell lung cancer”, Mayo Clin Proc. 2008 March; 83(3): 355-67.
2. Oze I et al, “Twenty-seven years of Phase III trials for patients with extensive disease small-cell lung cancer: Disappointing results”, PLoS One 2009; 4(11): e7835.
Linda Fugate is a scientist and writer in Austin, Texas. She has a Ph.D. in Physics and an M.S. in Macromolecular Science and Engineering. Her background includes academic and industrial research in materials science. She currently writes song lyrics and health articles.