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Cancer is described as a group of diseases with characters of aberrant proliferation and spread of abnormal cells, known as metastasis. If metastasis is not controlled, it can result in death, and often do so. Cancer is mainly caused by both external factors (carcinogens, chemicals, radiation, and infectious organisms) and internal factors (inherited mutations, hormonal disorder, immune conditions, and metabolism triggered mutations). These causal factors may act in tandem or in sequence to initiate or promote cancer. The development of most cancers requires several steps that occur and accumulate over many years. (Global Cancer Facts & Figures 2007). One in eight deaths in todayââ‚¬â„¢s world is due to cancer. Worldwide, cancer causes more deaths than AIDS (12.50% in comparison to 9.60%), malaria, and tuberculosis combined. Cancer is the second leading cause of death in economically developed countries (after heart diseases) and the third leading cause of death in developing countries (following diarrhoeal diseases and heart diseases) (Lopez et al.,2006)
Anyone is potential to develop cancer. However, the risk of being diagnosed with cancer increases with age. In economically developed countries, 78% of all newly reported cases of cancer occur at age 54 and older compared to that of 58% in developing countries. This difference is largely due to in age structure variation of the populations. The populations of developing countries are mostly composed of young individuals and have a smaller proportion of older individuals in whom cancer is most frequently manifests (Global Cancer Facts & Figures, 2007). As per the statistics, there have been more than 12 million cancer cases in 2007 all over the world, of which 5.4 million have occurred in economically developed countries and 6.7 million in economically developing countries. The approximate prevalence of different cancer among men and women in 2009 is given in Table-1/Figure-1. By 2050, the global burden of cancer is expected to rise to 27 million new cancer cases and 17.5 million cancer deaths, simply due to the growth and aging of the population (American Cancer Society, Inc., 2007). In economically developed countries, the three most commonly diagnosed cancers are bronchus, lung, prostate, and colorectal among men and breast, colorectal, and bronchus and lung among women. In economically developing countries, the three most commonly diagnosed cancers are bronchus and lung, liver, and stomach in men, and cervix uteri, breast, and stomach in women. In both economically developed and developing countries, the three most common cancers are also the three leading causes of cancer death (Jemal et al, 2010).
It is approximated that, 569,490 Americans will die from cancer, corresponding to greater than 1500 deaths per day. Cancers of the bronchus and lung, colorectum, and prostate in men, and cancers of the bronchus and lung, colorectum, and breast, in women will continue to be most common of the fatal cancers. These four cancers will account for approximately half of the total cancer deaths among men and women. Lung cancer exceeded breast cancer as the leading cause of cancer death in women in 1987 and is expected to account for 26% of all female cancer deaths in 2010 (Jemal et al, 2010). In a recent review, approximately 1.53 million new cases of cancer have been projected for the year 2010 in the US alone (excluding urinary bladder, basal cell and squamous cell cancers of the skin). Greater than 2 million unreported cases of basal cell and squamous cell skin carcinoma, approximately 54,010 cases of breast carcinoma in situ and 46,770 cases of melanoma in situ are expected to be newly diagnosed in 2010 (Jemal et al, 2010).
Cancer in children accounts for no more than 2% of all cancers, yet they continue to be one of the leading causes of childhood death in developed countries such as the USA. Cancer is the second most common (~12%) cause of death among children between the ages of 1 and 14 years in the United States, exceeded only by accidents. Over the past 25 years, significant improvements have been made in the 5-year relative survival rate for all of the major childhood cancers (Jemal et al, 2010). Leukemia continues to be the most common form of cancer for children in most countries except in Africa, where Kaposi sarcoma and Burkitt lymphoma are more prevalent (Pisani et al, 2006). There were 161,000 cancer cases among children aged 0-14 in 2007 (Fig. 2; (Source: Cancer Atlas, 2006.) Mortality from childhood cancer in general (particularly childhood leukemia), has sharply fallen in economically developed countries over the last 40 years. In the economically developed part of the world, overall five-year childhood cancer survival rates are about 75%. Among the 11 main childhood cancer types, European five-year survival rates are similar to those in the United States with the exception to neuroblastoma, renal tumors, bone tumors, and soft tissue sarcomas, for which survival is little higher in the US (Sankila et al., 2006).
In 2009, an estimated 192,370 new cases of invasive breast cancer have been reported among women, as well as an estimated 62,280 additional cases of in situ breast cancer. In 2009, approximately 40,170 have died from breast cancer. While, an estimated 1.3 million new cases of invasive breast cancer had occurred among women in 2007 out of which, an estimated 465,000 breast cancer deaths in women happened in 2007. Five-year survival from breast cancer is about 89% in the United States and 76% in Europe. Survival rates in developing countries are generally lower in comparison to Europe and North America (Breast Cancer Facts & Figures 2009-2010). Over the past 25 years, breast cancer incidence rates have risen approximately 30% in westernized countries because of changes in reproductive patterns and more recently because of increased screening (Parkin DM, 2005).
In the last two year, colorectal cancer was the fourth most common cancer in men and the third in women. All over the world, nearly 1.2 million cases of colorectal cancer occurred in 2007. The highest incidence rates were found in Japan, North America, parts of Europe, New Zealand, and Australia. Rates were low in Africa and South-East Asia. Rates were substantially higher in men than in women (Colorectal Cancer Facts & Figures 2006-2008).
Despite some improvements in surgical techniques and combinatorial therapies over the last several decades, lung cancer remains one of the most lethal cancers. Over the world, lung cancer is the chief cause of cancer death in men and the second leading cause of cancer death in women, with about 975,000 men and 376,000 women died from it in 2007, smoking being the primary cause of lung cancer among men, while indoor air pollution and passive smoking being the main cause among women (Lung Cancer Facts & Figure: Swierzewski; 2007).
There were 529,000 cases recorded in 2007 worldwide. The incidence rates of oesophageal cancer vary internationally by more than 50-fold. Highest rates are found in East and South Africa and Asia, including China and Central Asia. About 442,000 people will die from oesophageal cancer in 2007, with 85% of these deaths occurring in developing countries. The highest risk areas of the world are in Asia, stretching from northern Iran through the central Asian republics to North-Central China. Here and in other high-risk areas in South Africa and Northern France, most cases are squamous cell carcinomas (National Center for Health Statistics, 2006).
Prostate cancer is the second most frequently diagnosed cancer in men, with 782,600 new cases in 2007. The highest rates are recorded in the United States, the main reason being, the frequent testing of prostate specific antigen (PSA) which detects clinically important tumours as well as other slow-growing cancers that might otherwise escape diagnosis (Jemal. A et al, 2010).
Stomach cancer was the fourth most common malignancy in the world in 2007, with an estimated one million occurrences. Nearly 70% of them were in developing countries. About 800,000 people worldwide have died from stomach cancer in 2007 (Global Cancer Facts & Figures 2007). Worldwide, around 990,000 people were identified with stomach cancer in 2008. In 2006 there were around 86,000 new cases of stomach cancer reported in the European Union alone. Worldwide, around 738,000 people died from stomach cancer in 2008 (Cancer Research UK, 2010).
Liver cancer is the fifth most common cancer in men and the eighth in women. An estimated 711,000 new liver cancer cases will occur in the world during 2007. More than 80% of these cases occur in developing countries, with China alone being responsible for over 55% of the total. Rates are twice more higher in men as compared to women. Liver cancer rates are the highest in West and Central Africa and in Asia. In contrast, incidence rates are lowest in developed countries, with Japan being the exception (Global Cancer Facts & Figures 2007).
Cervical cancer is the second most commonly diagnosed cancer in women. An estimated 555,100 cases were recorded worldwide during 2007. More than 80% of these cases occurred in developing countries. Worldwide, the highest incidence rates are in Central and South America, the Caribbean, Sub-Saharan Africa, and Southern Asia. Rates are lowest in the Middle East, most of China, and Australia. The incidence and mortality rates from cervical cancer remain high in many parts of Central and South America, Africa, and Asia. Vaccination against human papilloma virus (HPV) is expected to have a significant impact on future rates in these regions (Global Cancer Facts & Figures 2007).
It is estimated that 44,670 men and women (10,740 men and 33,930 women) will be diagnosed with and 1,690 men and women will die of cancer of the thyroid in 2010 (Altekruse et al., 2010). From 2003-2007, the median age at diagnosis for cancer of the thyroid was 49 years of ageX Close
Table I-11 (http://seer.cancer.gov/csr/ 1975_2007/results_single/ sect_01_table.11_2pgs.pdf). Approximately 1.8% was diagnosed under age 20; 16.3% between 20 and 34; 21.5% between 35 and 44; 24.1% between 45 and 54; 17.6% between 55 and 64; 11.2% between 65 and 74; 6.1% between 75 and 84; and 1.4% 85+ years of age. In 2010, an estimated 44,670 adults (10,740 men and 33,930 women) in the USA will be diagnosed with cancer in thyroids. It is estimated that 1,690 deaths (730 men and 960 women) from this disease will occur in the present year. Thyroid cancer is also the fifth most common cancer in women (Cancer Facts & Figures, 2010).