Many people don’t know that cancer isn’t a single disease. It is in fact the name given to a class of diseases characterized by the abnormal and uncontrolled growth of cells. There are more than 200 types of cancers, each classified on the basis on the cell that is initially affected. According to the American Cancer Society, cancer is the second leading cause of death in the United States, accounting for almost one in every four deaths. The most recent data of the World Health Organization estimates that globally, four million new cases of cancer, along with 8.2 million cancer-related deaths were recorded in 2012.
In this article, we elaborate information about the symptoms, causes, prognosis and recent developments in the diagnosis and treatment of cancer.
What Does Cancer Do?
Cancer causes harm when abnormal ‘out-law’ cells divide uncontrollably to form masses of tissue, more commonly known as ‘tumors’. This happens in all forms of cancers, except leukemia (blood cancer), where the normal division of cells in the blood stream is prohibited.
Tumors interfere with almost every system of the body, such as the digestive, circulatory and nervous systems. Moreover, they release their own hormones that alter normal body mechanisms. Tumors are generally of two types: benign (demonstrate limited and localized growth) and malignant. The latter tend to be the more dangerous ones, resulting from any one of the following:
- a cancerous cell circulates within the body, using the lymphatic or blood system, and destroys healthy tissue via ‘invasion’
- a cells divides and grows uncontrollably and forms new blood vessels for receiving nutrition in a process called ‘angiogenesis’
A tumor that spreads to other parts of the body, invading and destroying healthy tissue in the process, is said to have metastasized, and the process is known as metastasis – a very serious condition that is extremely difficult to treat.
How Does Cancer Spread?
The October 2012 issue of Nature Communications reports a vital clue relating to the spread of cancer – a property known as ‘adhesion’ (stickiness) seems to be involved. Specific molecular interactions between cells and the extracellular matrix cause them to become ‘unstuck’ at the site of the original tumor, making them dislodge and move on to become attached to a new vulnerable site.
Researchers claim that this discovery is significant since cancer mortality – almost 90 percent – is primarily due to metastatic tumors, also known as secondary tumors or growths.
How Are Malignant And Non-Malignant Cells Different?
According to a study published in the April 2013 issue of Scientific Reports by the Physical Sciences-Oncology Centers, USA, malignant cells are much more flexible than non-malignant ones. They can easily squeeze through small gaps and apply a far greater force on the surrounding environment as compared to non-malignant and healthy cells.
The scientists, in collaboration with others, have created a catalogue enlisting the chemical and physical features of cancerous cells. They believe that the compilation will aid oncologists in detecting cancerous cells early on, and preventing metastasis.
How Are Different Cancers Classified?
There are broadly five groups into which the different forms of cancer have been classified.
- Carcinoma – cells that cover external and internal parts of the body. Examples include breast, lung and colon cancer
- Sarcoma – cells located in the cartilage, bone, fat, muscle, connective tissue and other supportive tissues
- Lymphoma – cancers that originate in lymph nodes and tissues of the immune system
- Leukemia – cancers that originate in the bone marrow and usually accumulate in the blood
- Adenoma – cancers that originate in the pituitary gland, adrenal gland, thyroid, and other glandular tissues
What Is The Nomenclature Of Cancers?
Usually, cancers are referred to with names that have a prefix related to the cell in which the cancer originated. The suffix is may be -sarcoma, -carcinoma, or simply -oma. Some common prefixes include:
- Adeno- (gland)
- Hemangio- (blood vessels)
- Lipo- (fat)
- Melano- (pigment cell)
- Myelo- (bone marrow)
- Chondro- (cartilage)
- Myo- (muscle)
- Osteo- (bone)
- Hepato- (liver)
- Lympho- (white blood cell)
- Retino- (eye)
- Neuro- (brain)
- Uro- (bladder)
- Erythro- (red blood cell)
What Are The Causes Of Cancer?
As explained previously, cancer is caused by the uncontrollable and abnormal growth of cells that fail to comply with the orderly patterns of growth, division and death. The natural process of programmed cell death – apoptosis – breaks down within these cells hence they do not die and continue to divide, forming heaps called tumors.
The different causes of cancer include:
· Mutations Within Genes Controlling Cell Growth
Abnormal cell growth can be caused by specific mutations to DNA, which in turn leads to gene alterations affecting cell division. There are four main genes involved in regulating the process of cell division:
1. Oncogenes that stimulate cells to divide
2. Tumor suppressor genes that inhibit cell division
3. Suicide genes that control apoptosis and stimulates cells to kill themselves in case of an abnormality
4. DNA-repair genes that instruct cells to repair any damages to DNA
Cancer occurs when mutations in any of these genes impairs the body’s normal mechanisms of suppressing cell growth and division, leading to the formation of a tumor.
Environmental Factors – Carcinogens
Carcinogens are substances such as toxins or chemicals that cause direct damage to the DNA, promoting the development of cancer. Examples include tobacco, asbestos, arsenic, radiation such as gamma and x-rays, the sun, and compounds in car exhaust fumes. Exposure to these substances produces free radicals within the body, which impair the functioning of normal body mechanisms.
Some types of cancers can also be inherited from family members via altered genes. It is also possible to be born with a genetic mutation or a faulty gene that increases one’s likelihood of developing cancer later in life.
With age, the likelihood of cancer-causing mutations within DNA increases. Hence, age is an important risk factor to consider as well.
Several viruses have also been associated with suppressing the immune system and the development of cancer. These include:
– Human papillomavirus (cervical cancer)
– Hepatitis B and C (liver cancer)
– Epstein-Barr virus (certain childhood cancers)
– Human Immunodeficiency Virus (HIV)
· Certain Foods
Recent research has also implicated certain foods to be involved in the development of cancer. These include:
– Mint, products containing menthol, spicy foods, fast food, carbonated drinks (stomach and esophagus cancer)
– Sausages, bacon, smoked meat, cheese spreads (colon cancer)
– Beef fat, fat milk, lard, fatty and greasy foods (breast cancer)
What Are The Symptoms Of Cancer?
The symptoms of cancer vary according to the location, spread, and size of the tumor. Here’s a general characterization:
- Certain cancers can be felt via physical examination, such as a lump on the breast or testicle
- Skin cancers (myelomas) are often identified by an abnormal wart or mole on the skin
- Oral cancers present as white patches within the mouth or as white spots on the tongue
- Brain tumors tend to present symptoms early on in the disease in the form of impaired cognitive functions
- Pancreatic cancers often have insignificant symptoms and are not identified until the tumor causes severe pain by pushing against nerves or by interfering with liver functions (jaundice)
- Some cancers tend to develop worsening symptoms as the tumor grows and pushes against vital blood vessels and organs. For example, colon cancer tends to cause constipation, diarrhea, and changes in stool size. Bladder or prostate cancer causes changes in bladder function
- Since cancerous cells use the body’s energy and interfere with hormonal function, symptoms such as fatigue, fever, increased sweating, anemia, and sudden weight loss are common. However, the latter may also develop in other diseases and should be carefully examined
- After metastasis, additional symptoms often develop in newly affected areas. This most significantly includes swollen or enlarged lymph nodes. Symptoms generally depend on the site of metastasis
- Cancers that affect or spread to the brain may cause vertigo, seizures or headaches
- Cancers that spread to the lungs may cause coughing or shortness of breath
- Liver enlargement, jaundice and brittle bones may also develop
How Is Cancer Diagnosed?
Early diagnosis and treatment can significantly improve outcomes and survival rates. Techniques of diagnosis include:
- Imaging techniques – X-rays, CT scans, MRI scans, PET scans, and ultrasound scansare used to detect the location of tumors and any organs it may be affecting
- Endoscopy – inserting a thin tube with a camera at one end inside the body to look for abnormalities
- Biopsy – extracting cancerous cells and observing them under the microscope
- Biochemical analysis – sugars, fats, proteins, and DNA at the molecular level; specific tests such as levels of PSA (prostate-specific antigen) in the bloodstream to diagnose prostate cancer
- Blood tests – this is a recent non-invasive development which could possibly save money and save many lives. In a trial study, the test was able to accurately diagnose suspected cases of lung cancer in 70 percent of the cases
What Are The Strategies For Treating Cancer?
Treatment depends mainly on the type of cancer, its progression and spread, age, personal characteristics and health status. Patients usually receive a combination of different therapies along with palliative care. The strategies used to treat cancer include the following:
In cases where the cancer has not spread, it is possible to completely cure the patient by surgically removing the tumor. Surgery is common for prostate, breast and testicle cancer. Surgery can also play a vital role in controlling certain symptoms, such as bowel obstruction and spinal cord compression.
Radiation treatment destroys cancerous cells using high-energy gamma rays or high-energy X-rays. Focusing these rays on the cells shrinks their size and damages their molecular makeup, causing them to commit suicide. Early radiotherapy was not very sophisticated and damaged healthy tissues and cells as well. However, modern techniques have improved the targeting of the beams to limit any adverse side-effects.
Chemotherapy uses chemicals that inhibit cell division by damaging proteins or DNA, hence stimulating suicide of cancerous cells. This treatment targets rapidly dividing cells, including healthy cells; however the latter are able to recover from the chemical-induced damage. Chemotherapy is generally used when the cancer has metastasized, and is a necessary treatment for certain forms of leukemia and lymphoma.
Chemotherapy is administered in cycles so that the body has time to recover between doses. Symptoms such as hair loss, fatigue, nausea and loss of appetite, darkening of skin and vomiting are common.
Immunotherapy helps the immune system fight cancer. There are two types: local immunotherapy which injects a treatment into the affected area to cause inflammation and shrink the tumor, and systemic immunotherapy which administers an agent, such as the protein interferon alpha into the entire body to shrink tumors.
Non-specific immunotherapy helps improve the cancer-fighting abilities of the body by stimulating the entire immune system to destroy cancer cells. However, these therapies are still developing and researchers have successfully introduced antibodies into the body that were able to inhibit the development of breast cancer cells.
· Hormone Therapy
Hormone therapy alters the hormone production of the body, inhibiting the growth of cancerous cells and killing them completely. Several forms of cancer, most prominently breast and prostate cancer have been linked with certain hormones. Breast cancer hormone therapies usually focus on reducing estrogen levels, whereas prostate cancer hormone therapies focus on reducing the levels of testosterone. Also, certain cases of leukemia and lymphoma can be treated using the hormone cortisone.
· Gene Therapy
Gene therapy aims to replace mutated genes with functional copies, hence addressing the root cause of cancer. Researchers are currently trying to replace the damaged gene that signals cells to stop dividing (p53 gene) with a copy of a working gene. Other gene therapies focus on further damaging cancerous cells to stimulate cell suicide.
This field is still in its infancy and no successful results have yet been reported.
Can Cancer Be Prevented?
Apart from factors such as age and genetic predispositions, the following aspects are important to consider in preventing the development of cancer:
– Systematic screening for detecting minor irregularities or lumps is among the best ways to prevent the progression of cancer and get early treatment. These include breast self-examination, mammograms, testicular self-examination, and Pap smears
– Lifestyle modifications – quitting smoking, reducing alcohol intake – can significantly lower the likelihood of many types of cancer, such as throat, lung, liver and mouth cancer
– Skin cancer can be prevented by limiting exposure to UV rays and using sunscreen
– Dietary modifications play a vital role; consuming diets low in fats and rich in fruits and vegetables and whole grains are recommended by physicians
– Certain vaccinations may also prevent some forms of cancer: a vaccination for the human papillomavirus could reduce the risk of developing cervical cancer in women, hepatitis B vaccines could prevent liver cancer
– Researchers from Northwestern University Feinberg School of Medicine in Chicago reported in the journal Circulation that the seven ways to prevent heart diseases could also help reduce the risk of cancer. These include eating healthy, being physically active, managing cholesterol levels and blood pressure, controlling blood sugar and saying no to smoking.