Lung cancer major site

Cancer is a major health issue worldwide. The most common solid tumors are breast, colorectal, ovarian, prostate and lung cancer, which account for more than 3.2 million new cases annually, and 1.7 million deaths each year [1]. In addition, large numbers of individuals are diagnosed with and die each year from hematological malignancies such as lymphomas (>166000 new cases and 93 000 deaths, respectively) or leukemias (144000 new cases and 109000 deaths, respectively). Early detection combined with advances in surgery and external radiotherapy have improved the prognosis for many patients with solid tumors in which the disease is confined to the primary anatomical site, but the outlook for patients with advanced disseminated cancer remains poor. Lymphomas and leukemias are more... 

The annual incidence rates (crude and age-standardized) and the numbers of new cases of cancers at 18 major sites in 1985 were estimated for 24 areas of the world [1] the data for the IS commonest cancers in men and women are summarized in Table 16.1. Lung cancer is the commonest cancer in men and the incidence rates are increasing in both developed and developing countries it is now the 3rd commonest cancer among women in North America and the 5th commonest worldwide. Breast cancer is still the commonest cancer in women, followed by cancer of the cervix. Wruldwide, cancers of the colon and rectum are the 3rd commonest cancers in both sexes. Canco s of the urinary bladder and pancreas are more common in developed than in developing countries. The incidence of lymphoma appears to be increasing. 

Cancer is the major latent harmful effect produced by ionizing radiation and the one that most people exposed to radiation are concerned about. The ability of alpha, beta, and gamma radiation to produce cancer in virtually every tissue and organ in laboratory animals has been well-demonstrated. The development of cancer is not an immediate effect. In humans, radiation-induced leukemia has the shortest latent period at 2 years, while other radiation induced cancers have latent periods >20 years. The mechanism by which cancer is induced in living cells is complex and is a topic of intense study. Exposure to ionizing radiation can produce cancer at any site within the body however, some sites appear to be more common than others, such as the breast, lung, stomach, and thyroid. 

Two types of epidemiological relationships have been found in two different populations. Both relationships were inverse to selenium bioavailability and paralleled the results from animal studies. In one type of study, selenium bioavailability has been inversely related to human cancer mortality in American cities and states (14-15). Schrauzer et.al. correlated the age-adjusted mortality from cancer at 17 major body sites with the apparent dietary selenium intakes estimated from food consumption data in 27 countries (16). Significant inverse correlations were observed for cancers of the large intestine, rectum, prostate, breast, ovary, lung, and leukemia. In addition, weaker inverse associations were found for cancers of the pancreas, skin, and bladder. 

Table 16.2 shows the sites at which cancer is most frequent and some of the known risk factors associated with these cancers. For some sites — lung, mouth/pharynx, liver, esophagus, bladder and leukemia — several risk factors have been identified but for other sites — stomach, breast, colon/rectum, lymphoma, prostate — the epidemiological evidence is far from conclusive. On the basis of present knowledge, the smoking and chewing of tobacco are clearly the major preventable causes of cancer. 

Primary and secondary malignant hepatic tumors are a major health problem worldwide. While metas-tases are common in western countries, primary liver cancers are frequently diagnosed in Asia and Africa. However, recent data suggest that the incidence and mortality of hepatocellular carcinoma (HCC) in Western nations are on the rise (Taylor-Robinson et al. 1997 Llovet et al. 2003). Likewise, the liver is the most common site for metastases. In 25%-50% of patients with malignancies liver metastases were observed at autopsy (Bernardino et al. 1982). The most frequent primary sites are colon, breast, pancreas, and lung. In the case of colorectal metastatic disease, the liver is the only metastatic site in 20%-30% of patients (Sasson and Sigurdson 2002). 

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