What is Cancer?
Cancer is a class of diseases characterized by out-of-control cell growth. There are over 100 different types of cancer, and each is classified by the type of cell that is initially affected.More dangerous, or malignant, tumors form when two things occur:Cancer harms the body when damaged cells divide uncontrollably to form lumps or masses of tissue called tumors (except in the case of leukemia where cancer prohibits normal blood function by abnormal cell division in the blood stream). Tumors can grow and interfere with the digestive, nervous, and circulatory systems, and they can release hormones that alter body function. Tumors that stay in one spot and demonstrate limited growth are generally considered to be benign.
- a cancerous cell manages to move throughout the body using the blood or lymph systems, destroying healthy tissue in a process called invasion
- that cell manages to divide and grow, making new blood vessels to feed itself in a process called angiogenesis.
When a tumor successfully spreads to other parts of the body and grows, invading and destroying other healthy tissues, it is said to have metastasized. This process itself is called metastasis, and the result is a serious condition that is very difficult to treat.
What are the Risk factors?
A risk factor is anything that increases a person`s chance of developing cancer. Different cancers have different risk factors. Use of tobacco, certain diets, alcohol, exposure to ultraviolet (UV) radiation, and to a lesser extent, exposure to cancer causing agents (carcinogens) in the environment and the workplace are some of the potential catalysts of cancer. It is important to remember, however, that these factors increase a person`s risk but do not always "cause" the disease.
Environmental Risk Factors
High levels of radiation like those from radiation therapies and x-rays (repeated exposure) can damage normal cells and increase the risk of developing leukemia, as well as cancers of the breast, thyroid, lung, stomach and other organs.
Ultraviolet (UV) Radiation
UV radiation from the sun are directly linked to melanoma and other forms of skin cancer. These harmful rays of the sun cause premature aging and damage the skin. Artificial sources of UV radiation, such as sun lamps and tanning booths, also increase the risk of skin cancer. By wearing protective clothing and sunscreens and by avoiding prolonged exposure to the sun, one may reduce the risk of skin cancer.
Some viruses, including hepatitis B and C, human papillomaviruses(HPV), and the Epstein Barr virus, which causes infectious mononucleosis, have been associated with increased cancer risk. Immune system diseases, such as AIDS, can make one more susceptible to some cancers.
Long term exposure to chemicals such as pesticides, uranium, nickel, asbestos, radon and benzene can increase the risk of cancer. Such carcinogens may act alone or in combination with another carcinogen, such as cigarette smoke, to increase the risk of cancer and other lung diseases.
Cigarette smoking and regular exposure to tobacco smoke greatly increase lung cancer. Cigarette smokers are more likely to develop several other types of cancer like those of the mouth, larynx, esophagus, pancreas, bladder, kidney and cervix. Smoking may also increase the likelihood of developing cancers of the stomach, liver, prostate, colon and rectum. The use of other tobacco products, such as chewing tobacco, are linked to cancers of the mouth, tongue and throat. The risk of cancer decreases soon after a smoker quits, while precancerous conditions often diminish after a person stops using smokeless tobacco.
Heavy drinkers face an increased risk of cancers of the mouth, throat, esophagus, larynx and liver. Some studies suggest that even moderate drinking may slightly increase the risk of breast cancer. All cancers caused by cigarette smoking and heavy use of alcohol could be prevented completely.
High-fat, high cholesterol diets are proven risk factors for several types of cancer such as those of the colon, uterus and prostate. Obesity may be linked to breast cancer among older women as well as to cancers of the prostate, pancreas, uterus, colon and ovary. Many cancers that are related to dietary factors could be prevented. Healthy food choices and a well balanced diet including fiber, vitamins, minerals and low fat items may help to reduce cancer risk.Certain cancers are related to viral infections-for example, hepatitis B virus (HBV), human papillomavirus (HPV), human immunodeficiency virus (HIV), human T-cell leukemia/lymphoma virus-I (HTLV-I), and others-that can be prevented through behavioral changes.
Regular screening examinations by a health care professional can result in the detection of cancers of the breast, colon, rectum, cervix, prostate, testis, oral cavity, and skin at an earlier stage, when treatment is more likely to be successful. Self-examinations for cancers of the breast and skin may also result in detection of tumors at early stages. The screening-accessible cancers listed above account for about half of all new cancer cases.
The 5-year relative survival rate for these cancers is about 80%. If everyone participated in regular cancer screenings, this rate could increase to 95%.
HereDitary Risk Factors
Twenty percent of cancers are hereditary. This means that the abnormal gene responsible for causing cancer is passed from parent to child, posing a greater risk for that type of cancer in all descendants of the family. However, just because someone has a cancer-causing gene doesn`t mean they will automatically get cancer. If hereditary cancer is suspected, family members should consider genetic counseling and testing to determine their risk. If diagnosed in the early stages, such cancers are most responsive to treatment.Signs of hereditary cancer include;
A theory exists with some scientific support, that certain smokers have a higher risk of smoking-induced lung cancer than others because of their genetic make-up.
Some cancers are more common among certain ethnic groups.
Many cancers are associated with having a family history of that cancer. Breast, ovarian, prostate and colon are some of these cancers.
What are the Signs and symptoms?
Unexplained weight loss
Signs and symptoms of certain cancers
Change in bowel habits or bladder function
Sores that do not heal
White patches inside the mouth or white spots on the tongue
Unusual bleeding or discharge
Thickening or lump in the breast or other parts of the body
Indigestion or trouble swallowing
Recent change in a wart or mole or any new skin change
Nagging cough or hoarsenessMost cancers are initially recognized either because signs or symptoms appear or through screening. Neither of these lead to a definitive diagnosis, which usually requires the opinion of a pathologist, a type of physician (medical doctor) who specializes in the diagnosis of cancer and other diseases.
How is Cancer diagnosed?
People with suspected cancer are investigated with medical tests. These commonly include blood tests, X-rays, CT scans and endoscopy.
A cancer may be suspected for a variety of reasons, but the definitive diagnosis of most malignancies must be confirmed by histological examination of the cancerous cells by a pathologist. Tissue can be obtained from a biopsy or surgery. Many biopsies (such as those of the skin, breast or liver) can be done in a doctor's office. Biopsies of other organs are performed under anesthesia and require surgery in an operating room.
The tissue diagnosis given by the pathologist indicates the type of cell that is proliferating, its histological grade, genetic abnormalities, and other features of the tumor. Together, this information is useful to evaluate the prognosis of the patient and to choose the best treatment. Cytogenetics and immunohistochemistry are other types of testing that the pathologist may perform on the tissue specimen. These tests may provide information about the molecular changes (such as mutations, fusion genes, and numerical chromosome changes) that has happened in the cancer cells, and may thus also indicate the future behavior of the cancer (prognosis) and best treatment.
How is cancer treated?
Cancer treatment depends on the type of cancer, the stage of the cancer (how much it has spread), age, health status, and additional personal characteristics. There is no single treatment for cancer, and patients often receive a combination of therapies and palliative care. Treatments usually fall into one of the following categories: surgery, radiation, chemotherapy, immunotherapy, hormone therapy, or gene therapy.
Surgery is the oldest known treatment for cancer. If a cancer has not metastasized, it is possible to completely cure a patient by surgically removing the cancer from the body. This is often seen in the removal of the prostate or a breast or testicle. After the disease has spread, however, it is nearly impossible to remove all of the cancer cells. Surgery may also be instrumental in helping to control symptoms such as bowel obstruction or spinal cord compression.
Radiation treatment, also known as radiotherapy, destroys cancer by focusing high-energy rays on the cancer cells. This causes damage to the molecules that make up the cancer cells and leads them to commit suicide. Radiotherapy utilizes high-energy gamma-rays that are emitted from metals such as radium or high-energy x-rays that are created in a special machine. Early radiation treatments caused severe side-effects because the energy beams would damage normal, healthy tissue, but technologies have improved so that beams can be more accurately targeted. Radiotherapy is used as a standalone treatment to shrink a tumor or destroy cancer cells (including those associated with leukemia and lymphoma), and it is also used in combination with other cancer treatments.
Chemotherapy utilizes chemicals that interfere with the cell division process - damaging proteins or DNA - so that cancer cells will commit suicide. These treatments target any rapidly dividing cells (not necessarily just cancer cells), but normal cells usually can recover from any chemical-induced damage while cancer cells cannot. Chemotherapy is generally used to treat cancer that has spread or metastasized because the medicines travel throughout the entire body. It is a necessary treatment for some forms of leukemia and lymphoma. Chemotherapy treatment occurs in cycles so the body has time to heal between doses. However, there are still common side effects such as hair loss, nausea, fatigue, and vomiting. Combination therapies often include multiple types of chemotherapy or chemotherapy combined with other treatment options.
Immunotherapy aims to get the body's immune system to fight the tumor. Local immunotherapy injects a treatment into an affected area, for example, to cause inflammation that causes a tumor to shrink. Systemic immunotherapy treats the whole body by administering an agent such as the protein interferon alpha that can shrink tumors. Immunotherapy can also be considered non-specific if it improves cancer-fighting abilities by stimulating the entire immune system, and it can be considered targeted if the treatment specifically tells the immune system to destroy cancer cells. These therapies are relatively young, but researchers have had success with treatments that introduce antibodies to the body that inhibit the growth of breast cancer cells. Bone marrow transplantation (hematopoetic stem cell transplantation) can also be considered immunotherapy because the donor's immune cells will often attack the tumor or cancer cells that are present in the host.
Several cancers have been linked to some types of hormones, most notably breast and prostate cancer. Hormone therapy is designed to alter hormone production in the body so that cancer cells stop growing or are killed completely. Breast cancer hormone therapies often focus on reducing estrogen levels (a common drug for this is tamoxifen) and prostate cancer hormone therapies often focus on reducing testosterone levels. In addition, some leukemia and lymphoma cases can be treated with the hormone cortisone.
The goal of gene therapy is to replace damaged genes with ones that work to address a root cause of cancer: damage to DNA. For example, researchers are trying to replace the damaged gene that signals cells to stop dividing (the p53 gene) with a copy of a working gene. Other gene-based therapies focus on further damaging cancer cell DNA to the point where the cell commits suicide. Gene therapy is a very young field and has not yet resulted in any successful treatments.