CANCER

CLASSIFICATION, SIGN AND SYMPTOMS, TREATMENT, PREVENTION.

WHAT IS CANCER?• Cancer (medical term: malignant neoplasm) is a class of diseases in which a

group of cell display uncontrolled growth through division beyond normal limits, invasion that intrudes upon and destroys adjacent tissues, and sometimes metastasis, which spreads the cells to other locations in the body via lymph or blood. These three malignant properties of cancers differentiate them from benign tumors, which are self-limited, and do not invade or metastasize.

• Cancers are primarily an environmental disease with 90-95% of cases due to lifestyle and environmental factors and 5-10% due to heredity.1. Common environmental factors leading to cancer death include:

• tobacco:- (25-30%),diet and obesity:- (30-35%),infections:- (15-20%), radiation, stress, lack of physical activity, and environmental pollutants.[1]These environmental factors cause abnormalities in the genetic material of cells.[2]Genetic abnormalities found in cancer typically affect two general classes of genes oncogene sand tumor suppressor genes.

• Definitive diagnosis requires the examination of a biopsy specimen, although the initial indication of malignancy can be symptomatic or radiographic. Most cancers can be treated and this may include chemotherapy and radiotherapy and/or surgery. The prognosis is most influenced by the type of cancer and the extent of disease. While cancer can affect people of all ages the risk typically increasing with age.[3] In 2004 cancer caused about 13% of all human deaths [4] (7.6 million).[5]

WHAT IS CANCER?

Cancers are classified by the type of cell that resembles the tumor and, therefore, the tissue presumed to be the origin of the tumor. These are the histology and the location, respectively. Examples of general categories include:

• Carcinoma: Malignant tumors derived from epithelial cells. This group represents the most common cancers, including the common forms of breast, prostate, lung and colon cancer.

• Sarcoma: Malignant tumors derived from connective tissue, or mesenchymal cells.

• Lymphoma and leukemia: Malignancies derived from hematopoietic (blood-forming) cells

• Germ cell tumor: Tumors derived from totipotent cells. In adults most often found in the testicle and ovary; in fetuses, babies, and young children most often found on the body midline, particularly at the tip of the tailbone; in horses most often found at the poll (base of the skull).

• Blasti tumor or blastoma: A tumor (usually malignant) which resembles an immature or embryonic tissue. Many of these tumors are most common in children.

CLASSIFICATION

CLASSIFICATION OF CANCER

Signs and symptoms

Roughly, cancer symptoms can be divided into three groups:

• Local symptoms: unusual lumps or swelling (tumor), hemorrhage (bleeding), pain and/or ulceration. Compression of surrounding tissues may cause symptoms such as jaundice (yellowing the eyes and skin).

• Symptoms of metastasis (spreading): enlarged lymph nodes, cough and hemoptysis, hepatomegaly (enlarged liver), bone pain, fracture of affected bones and neurological symptoms. Although advanced cancer may cause pain, it is often not the first symptom.

• Systemic symptoms: weight loss, poor appetite, fatigue and cachexia (wasting), excessive sweating (night sweats), anemia and specific paraneoplastic phenomena, i.e. specific conditions that are due to an active cancer, such as thrombosis or hormonal changes.

Causes

• Cancers are primarily an environmental disease with 90-95% of cases due to environmental factors and 5-10% due to genetics.[1] "Environmental", as used by cancer researchers, means any cause that is not genetic, and includes everything from natural sunlight to industrial pollution to viruses to behavioral choices to old age. Most environmental causes, such as naturally occurring background radiation, are not modifiable or controllable. Common environmental factors that lead to cancer death include: tobacco (25-30% of deaths), diet and obesity (30-35%), infections (15-20%), radiation, stress, lack of physical activity, and environmental pollutants.[1]

Types of cancer

Causes of cancer

Skin cancer Lung cancer

Causes:- CHEMICALS• Cancer pathogenesis is traceable back to DNA mutations that impact cell growth and

metastasis. Substances that cause DNA mutations are known as mutagens, and mutagens that cause cancers are known as carcinogens. Particular substances have been linked to specific types of cancer. Tobacco smoking is associated with many forms of cancer, and causes 90% of lung cancer. Prolonged exposure to asbestos fibers is associated with mesothelioma.

• Many mutagens are also carcinogens, but some carcinogens are not mutagens. Alcohol is an example of a chemical carcinogen that is not a mutagen.[10] Such chemicals may promote cancers through stimulating the rate of cell division. Faster rates of replication leaves less time for repair enzymes to repair damaged DNA during DNA replication, increasing the likelihood of a mutation.

• Decades of research has demonstrated the link between tobacco use and cancer in the lung, larynx, head, neck, stomach, bladder, kidney, oesophagus and pancreas. Tobacco smoke contains over fifty known carcinogens, including nitrosamines and polycyclic aromatic hydrocarbons. Tobacco is responsible for about one in three of all cancer deaths in the developed world,[6] and about one in five worldwide.[12] Indeed, lung cancer death rates in the United States have mirrored smoking patterns, with increases in smoking followed by dramatic increases in lung cancer death rates and, more recently when?], decreases in smoking followed by decreases in lung cancer death rates in men. However, the numbers of smokers worldwide is still rising, leading to what some organizations have described as the tobacco epidemic.

• Cancer related to ones occupation is believed to represent between 2-20% of all cases. Every year, at least 200,000 people die worldwide from cancer related to their workplace. Millions of workers run the risk of developing cancers such as lung cancer and mesothelioma from inhaling asbestos fibers and tobacco smoke, or leukemia from exposure to benzene at their workplaces. Currently, most cancer deaths caused by occupational risk factors occur in the developed world.[15] It is estimated that approximately 20,000 cancer deaths and 40,000 new cases of cancer each year in the U.S. are attributable to occupation.

Causes:- CHEMICALS

Causes:-RADIATION

• Sources of ionizing radiation, such as radon gas, can cause cancer. Prolonged exposure to ultraviolet radiation from the sun can lead to melanoma and other skin malignancies. One report estimates that approximately 29 000 future cancers could be related to the approximately 70 million CT scans performed in the US in 2007. It is estimated that 0.4% of current cancers in the United States are due to CTs performed in the past and that this may increase to as high as 1.5-2% with 2007 rates of CT usage.

• Non-ionizing radio frequency radiation from mobile phones and other similar RF sources has also been proposed as a cause of cancer, but there is currently little established evidence of such a link.

Causes:-INFECTION• Some cancers can be caused by infection. This is especially true in animals such as birds,

but also in humans, with viruses responsible for up to 20% of human cancers worldwide.] These include human papillomavirus (cervical carcinoma), human polyomaviruses (mesothelioma, brain tumors), Epstein-Barr virus (B-cell lymphoproliferative disease and nasopharyngeal carcinoma), Kaposi's sarcoma herpes virus (Kaposi's Sarcoma and primary effusion lymphomas), hepatitis B and hepatitis C viruses (hepatocellular carcinoma), and Human T-cell leukemia virus-1 (T-cell leukemia's). Bacterial infection may also increase the risk of cancer, as seen in Helicobacter pylori induced gastric carcinoma.

• Experimental and epidemiological data imply a causative role for viruses and they appear to be the second most important risk factor for cancer development in humans, exceeded only by tobacco usage. The mode of virally induced tumors can be divided into two, acutely transforming or slowly transforming. In acutely transforming viruses, the virus carries an overactive oncogene called viral-oncogene (v-onc), and the infected cell is transformed as soon as v-onc is expressed. In contrast, in slowly transforming viruses, the virus genome is inserted near a proto-oncogene in the host genome. The viral promoter or other transcription regulation elements then cause over expression of that proto-oncogene. This induces uncontrolled cell division. Because the site of insertion is not specific to proto-oncogene and the chance of insertion near any proto-oncogene is low, slowly transforming viruses will cause tumors much longer after infection than the acutely transforming viruses.

• Hepatitis viruses, including hepatitis B and hepatitis C, can induce a chronic viral infection that leads to liver cancer in 0.47% of hepatitis B patients per year (especially in Asia, less so in North America), and in 1.4% of hepatitis C carriers per year. Liver cirrhosis, whether from chronic viral hepatitis infection or alcoholism, is associated with the development of liver cancer, and the combination of cirrhosis and viral hepatitis presents the highest risk of liver cancer development. Worldwide, liver cancer is one of the most common, and most deadly, cancers due to a huge burden of viral hepatitis transmission and disease.

INFECTION• Advances in cancer research have made a vaccine designed to prevent cancers

available. In 2006, the U.S. Food and Drug Administration approved a human papilloma virus vaccine, called Gardasil. The vaccine protects against 6,11,16,18 strains of HPV, which together cause 70% of cervical cancers and 90% of genital warts. It also lists vaginal and vulvar cancers as being protected. In March 2007, the US Centers for Disease Control and Prevention (CDC) Advisory Committee on Immunization Practices (ACIP) officially recommended that females aged 11–12 receive the vaccine, and indicated that females as young as age 9 and as old as age 26 are also candidates for immunization. There is a second vaccine from Cervarix which protects against the more dangerous HPV 16,18 strains only. In 2009, Gardasil was approved for protection against genital warts. In 2010, the Gardasil vaccine was approved for protection against anal cancer for males and reviewers stated there was no anatomical, histological or physiological anal differences between the genders so females would also be protected.

• In addition to viruses, researchers have noted a connection between bacteria and certain cancers. The most prominent example is the link between chronic infection of the wall of the stomach with Helicobacter pylori and gastric cancer. Although only a minority of those infected with Helicobacter go on to develop cancer, since this pathogen is quite common it is probably responsible for most of these cancers.

• HIV is associated with a number of malignancies, including Kaposi's sarcoma, non-Hodgkin's lymphoma, and HPV-associated malignancies such as anal cancer and cervical cancer. AIDS-defining illnesses have long included these diagnoses. The increased incidence of malignancies in HIV patients points to the breakdown of immune surveillance as a possible etiology of cancer. Certain other immune deficiency states (e.g. common variable immunodeficiency and IgA deficiency) are also associated with increased risk of malignancy.

INFECTION: HIV VIRUS INFECTION

HEREDITY• Most forms of cancer are sporadic, meaning that there is no inherited cause of the

cancer. There are, however, a number of recognized syndromes where there is an inherited predisposition to cancer, often due to a defect in a gene that protects against tumor formation. Famous examples are:

• certain inherited mutations in the genes BRCA1 and BRCA2 are associated with an elevated risk of breast cancer and ovarian cancer

• tumors of various endocrine organs in multiple endocrine neoplasia (MEN types 1, 2a, 2b)

• Li - Fraumeni syndrome (various tumors such as osteosarcoma, breast cancer, soft tissue sarcoma, brain tumors) due to mutations of p53

• Turcot syndrome (brain tumors and colonic polyposis)

• Familial adenomatous polyposis an inherited mutation of the APC gene that leads to early onset of colon carcinoma.

• Hereditary nonpolyposis colorectal cancer (HNPCC, also known as Lynch syndrome) can include familial cases of colon cancer, uterine cancer, gastric cancer, and ovarian cancer, without a preponderance of colon polyps.

• Retinoblastoma, when occurring in young children, is due to a hereditary mutation in the retinoblastoma gene.

• Down syndrome patients, who have an extra chromosome 21, are known to develop malignancies such as leukemia and testicular cancer, though the reasons for this difference are not well understood.

PREVENTION• Cancer prevention is defined as active measures to decrease the

incidence of cancer. The vast majority of cancer risk factors are environmental or lifestyle-related, thus cancer is largely a preventable disease. Greater than 30% of cancer is preventable via avoiding risk factors including: tobacco, overweight or obesity, low fruit and vegetable intake, physical inactivity, alcohol, sexually transmitted infection, air pollution.

• Examples of modifiable cancer risk factors include alcohol consumption (associated with increased risk of oral, esophageal, breast, and other cancers), smoking (80% of women with lung cancer have smoked in the past, and 90% of men), physical inactivity (associated with increased risk of colon, breast, and possibly other cancers), and being overweight / obese (associated with colon, breast, endometrial, and possibly other cancers). Based on epidemiologic evidence, it is now thought that avoiding excessive alcohol consumption may contribute to reductions in risk of certain cancers; however, compared with tobacco exposure, the magnitude of effect is modest or small and the strength of evidence is often weaker. Other lifestyle and environmental factors known to affect cancer risk (either beneficially or detrimentally) include certain sexually transmitted diseases (such as those conveyed by the human papillomavirus), the use of exogenous hormones, exposure to ionizing radiation and ultraviolet radiation from the sun or from tanning beds, and certain occupational and chemical exposures.

TREATMENT:- MEDICATION

• The concept that medications could be used to prevent cancer is an attractive one, and many high-quality clinical trials support the use of such chemoprevention in defined circumstances.

• Daily use of tamoxifen, a selective estrogen receptor modulator (SERM), typically for 5 years, has been demonstrated to reduce the risk of developing breast cancer in high-risk women by about 50%. A recent when?] study reported that the selective estrogen receptor modulator raloxifene has similar benefits to tamoxifen in preventing breast cancer in high-risk women, with a more favorable side effect profile.

• Raloxifene is a SERM like tamoxifen; it has been shown (in the STAR trial) to reduce the risk of breast cancer in high-risk women equally as well as tamoxifen. In this trial, which studied almost 20,000 women, raloxifene had fewer side effects than tamoxifen, though it did permit more DCIS to form.

• Finasteride, a 5-alpha-reductase inhibitor, has been shown to lower the risk of prostate cancer, though it seems to mostly prevent low-grade tumors. The effect of COX-2 inhibitors such as rofecoxib and celecoxib upon the risk of colon polyps have been studied in familial adenomatous polyposis patients and in the general population. In both groups, there were significant reductions in colon polyp incidence, but this came at the price of increased cardiovascular toxicity.

• As of 2010 vitamins have not been found to be effective at preventing cancer, while low levels of vitamin D is correlated with increased cancer risk. Whether this relationship is causal and vitamin D supplementation is protective is yet to be determined. Beta-carotene supplementation has been found to increase slightly, but not significantly risks of lung cance.Folic acid supplementation has not been found effective in preventing colon cancer and may increase colon polyps.

MEDICATION

VACCINATION

• Vaccines have been developed to prevent oncogenic infectious agents and therapeutic vaccines are in development to stimulate an immune response against cancer-specific epitopes.

• Human papillomavirus vaccine (Gardasil and Cervarix) decreases the risk of developing cervical cancer. The hepatitis B vaccine prevents infection with hepatitis B virus and thus decreases the risk of liver cancer

VACCINATION

RESEARCH

• Main article: Cancer research

• Cancer research is the intense scientific effort to understand disease processes and discover possible therapies. The improved understanding of molecular biology and cellular biology due to cancer research has led to a number of new, effective treatments for cancer since President Nixon declared "War on Cancer" in 1971. Since 1971 the United States has invested over $200 billion on cancer research; that total includes money invested by public and private sectors and foundations. Despite this substantial investment, the country has seen a five percent decrease in the cancer death rate (adjusting for size and age of the population) between 1950 and 2005.

• Leading cancer research organizations and projects include the American Association for Cancer Research, the American Cancer Society (ACS), the American Society of Clinical Oncology, the European Organization for Research and Treatment of Cancer, the National Cancer Institute, the National Comprehensive Cancer Network, and The Cancer Genome Atlas project at the NCI.

SO CANCER IS THREATNING DISEASE OF LIFE.

THANK YOU VERY MUCH