As part of our survival, new cells are made through cell division, and old or unwanted cells die. Sometimes cells divide and multiply faster than they are needed and bad cells that are supposed to die continue to live, causing damage to good cells. The overgrowth of cells produces the disease called cancer and the overgrown cells are referred to as tumors. Tumors may be benign or malignant. Benign means that they are localized, i.e. they don’t spread to other areas of the body. This makes them easy to remove and there is less chance of regrowth. Under a microscope, benign tumor cells look very uniform and similar to the original cells from which they develop. Malignant tumors cells are cells that metastasize (spread) to other areas of the body. It uses the lymphatic and blood circulatory system as its “highway” to travel to other body parts where they grow. Looking at malignant cells under a microscope, they tend to be non-uniformed and look very different from normal tissue cells around them.
Cancer is caused by mutations of genes responsible for cell growth and development. These are namely:
- Oncogenes: Type of genes that causes cells to divide uncontrollably. You may view these genes as a type of “cancer genes”
- Tumor Suppressant Genes: Suppress growth of tumors
- Suicide Genes: Tells infected or mal-functioning cells to die
- DNA Repair Genes: Prevent or repair DNA errors that may occur during cell replication
Cancer may occur if oncogenes are telling cells to divide when new cells are not needed, or due to under-activity of suicide or repair genes. Approximately 5-10% of cancers are due to inherited mutation of one or more of these genes. So, the majority of cancers are really acquired. That is, mutations occurring not due to inheritance, but due to environmental factors.
Types of Cancer
There are five major types of cancer
- Carcinoma: Cancer of skin cells and cells that line the surface of organs (epithelial cells) such as the liver, kidney, breast, prostate and pancreas. Most cancers (80-90%) are in this category
- Sarcoma: Cancer of supportive and connective tissue such as bones, tendons, cartilage and fat
- Myeloma: Cancer of plasma cells (B-Cells that makes antibodies) in the bone marrow.
- Lymphoma: Cancer of lymphocytes (B and T cells) and hence enlargement of the lymph nodes. Lymphomas are solid tumors.
- Leukemia: Cancer of white blood cells (leukocytes) in the blood and bone marrow. Leukemia tumors are liquid.
Risk Factors for Cancer
Top risk factors for cancer include:
- Age: The majority of people with cancer are over 55
- Tobacco Use: 30% of all cancer deaths is due to smoking
- Infection: Generally caused by viral infection e.g. human papillomavirus virus (hpv), hepatitis, Epstein-Barr virus, human herpes virus 8, human T-lymphotropic virus-I and helicobacter pylori
- Radiation: This includes ionizing radiation from the sun; medical radiation such as X rays, CT scans and nuclear medicine; and radon gas in homes
- Immunosuppressant Medication: Medication taken to reduce the activity of the immune system. These drugs are often used to help prevent rejection of organ transplant. However, since they suppress T cells that fight against cancer cells, patients run the risk of developing cancer during the treatment.
Cancer can be detected by looking for certain signs and symptoms e.g. unexplained weight loss, fatigue, fever, pain and unusual skin changes such as pigmentation and hair follicle growth. However, since these symptoms may also be associated with other diseases, the only way to be sure if you have cancer is to get tested. Diagnostic tools may include:
- Collecting personal and family history
- Doing a physical examination
- Conducting blood tests to check for cancer antigens
- Taking a biopsy to look for abnormal cells under the microscope
- Running diagnostic imaging to look for tumors e.g. X ray, CT scan, MRI and ultra sound
Common Signs and Symptoms of Cancer
Cancer comes with many signs and symptoms. No one will confirm cancer but pay attention to these and get checked if you have doubts
- Unexplained weight loss
- Extreme tiredness or breathlessness
- Skin changes
- Constant pain
- Bowel changes
- Bad cough
- Problem swallowing
Grading and Staging of Cancer
Grading and staging of cancer are done to determine how serious the cancer is. Grading is done particularly to describe how much the cancer cells have changed from the size, shape and appearance of the normal cells. Staging describes how much the cancer has spread.
One of the most common systems used to characterize the amount and spread of cancer in a patient’s body is the TNM staging system where TNM stands for tumor, node and metastasis respectively.
- TX: The tumor cannot be measured
- T0: There is no tumor
- Tis: The tumor is present but it is in situ (in place or localized)
- T1, T2, T3, T4: Cancer has spread. A higher number means more spread
- NX: Infection in node cannot be determined
- N0: No node is infected
- N1, N2, N3: Nodes are infected. A higher number means more nodes are infected
- MX: Metastasis cannot be determined
- M0: No metastasis
- M1: Cancer has metastasized
It is the combination of all these values in the TNM scoring system that will inform your physician whether you have stage 0, 1, 2, 3, or 4 cancer.
- Stage 0: Abnormal cells exists but there is no tumor
- Stage I (early stage cancer): Small and localized tumor is evident
- Stage II and III: Tumors are larger and has limited metastasis (a higher stage means more metastasis)
- Stage IV: There is significant metastasis beyond the original location. Prognosis is poor at this stage; usually no more than 5 years
Cancer may be treated by the following methods
- Surgery to remove cancerous tissue
- Radiation using focused high energy rays (usually X-rays and gamma rays) to kill cancer cells
- Chemotherapy using systemic drugs to kill cancer cells throughout the body. The procedure targets fast-growing cells which includes cancer cells, but some other cells that also grows fast are also killed e.g. red blood cells, hair follicle cells, and cells lining the digestive tract
- Hormone therapy to block natural hormones that “feeds” cancer cells. For example, estrogen increases the growth of breast cancer cells. Hormone treatment could include removing the ovaries or medication that control estrogen production in the body
- Immunotherapy using antibodies that targets cancer cells
Preventing/Reducing the Risk of Cancer
Consider the following suggestions to prevent or lower your risk of cancer
- Don’t use tobacco: Remember that 30% of all cancer deaths is due to tobacco use
- Eat healthy: Make sure to incorporate lots of different fruits and vegetables to get the benefits of phytochemicals (powerful disease-preventing chemicals in plants)
- Limit alcohol consumption or better yet, don’t drink at all
- Protect your skin from ultraviolet radiation. Use a sun screen
- Be physically active. People who are physically active have lower risk of cancer and they put up a better fight if they already have cancer
- Get immunized. Many viruses are agents for cancer. Make sure to get immunized from the human papillomavirus (hpv) since it causes cervical, penal, anal, and throat cancer.
- Don’t share needles
- Get cancer screening. Women should get a mammogram every 2 years after age 50 and pap smear every 3 years after age 21. Men should get prostate screening annually starting at age 40 if cancer runs in the family or 45 if they are African American. If they are low-risk they should start screening at least by age 50.