Radiation Therapy in Management of Small-Cell Lung Cancer

Abstract

Worldwide, lung carcinoma (LC) is the commonest and deadliest form of cancer in men and women, exceeding the mortality of prostate, breast, and colorectal cancers combined (Jemal et al., 2009). Irrespective of histologic subtype, more than 90% of all LC is strongly associated with cigarette smoking (Alavanja et al., 2002), and the risk significantly increases with the number of cigarettes smoked per day, degree of inhalation, age at initiation, and life-long cumulative exposure (Tyczynski et al., 2003). Although survival at 5-year is less than 15%, yet, there exists no single proven chemopreventive measure reducing the risk of LC development, except for cessation of cigarette smoking. Histologically, non-small cell LC (NSCLC) and small-cell LC (SCLC) are the two commonest types of LC, constituting 85-90% and 10-15% of all cases, respectively (Rosenzweig et al., 2010). SCLC (previously called oat cell carcinoma) is relatively less common than NSCLC; however, because of a more aggressive growth pattern and clinical course, its treatment is more challenging. Although there is no significant difference in outcome by histologic subtype, the World Health Organization classification subdivides SCLC into three cell types; pure or classic, variant cell, and mixed (Brambilla et al., 2001). SCLC displays a high propensity to metastasize, and usually a remarkable but temporary responsiveness to chemotherapy and radiotherapy (RT). Although some may be cured, most patients succumb to disease because of rapid development of drug resistance and resultant disease progression. Median survival for metastatic SCLC is only 10 months, which is interestingly very similar to patients with relatively much more drug resistant NSCLC of similar stage (Chute et al., 1997). Despite great improvements in imaging, pathology, genetics, chemotherapy, and RT techniques, this did not translate into the clinical outcomes, thus, the current overall survival rate for SCLC patients is not different than that was 20 years before (Chute et al., 1997). This chapter has been designated to focus specifically on treatment of SCLC patients, with specific emphasises on the technical basis and outcomes of current RT and concurrent chemoradiotherapy (C-CRT). Therefore, readers interested in more comprehensive information about the epidemiology, etiology, preventive measures, pathologic and genetic basis and surgical treatment of SCLC are referred to excellent reviews available in this book.