Cancer! Terrifying isn’t it? Just the word “cancer” strikes fear into the hearts of many if not all. Cancer is a far-reaching term. It describes the group of diseases that results when changes at the cellular level cause the uncontrolled growth and division of cells. It goes by many designations including malignant tumor, sarcoma, carcinoma, lymphonoma just to mention a few. The World Cancer Day falls on the 4th of February. Over hundred types of cancers affect humans. The word cancer is actually the Greek word for the decapod crustacean, the crab. Ancient Greek physicians Hippocrates and Galen, among others noted the similarity of the crab to the tumors found on cancer patients. A typical cell in the human body has specific functions and a fixed lifespan. For a cell to be termed cancerous, it must exhibit certain oddities which are contemporarily known as the six hallmarks of cancer.
The Six Hallmarks of Cancer
This idea was coined by Douglas Hanahan and Robert Weinberg in their paper, ‘The Hallmarks of Cancer’ published in the year 2000. These hallmarks constitute the six biological characteristics acquired during malignant progression (the development of a malignant tumor). They are;
1. Cell growth and division without the proper signals or Self-sufficiency in growth signals. Normal cells divide, but have numerous important controls on that growth. They grow only when stimulated by growth factors. Cancer cells however, have the ability to grow and divide without these external signals.
2. Continuous growth and division given contrary signals or insensitivity to anti-growth signals. If a cell is damaged, a molecular brake prevents further division of that cell. Certain proteins, known as tumor suppressor genes halt the division of a cell if the DNA within it is altered. Cancer cells are generally resistant to growth-preventing signals from their neighbours. They also lack contact inhibition and will continue to grow and divide regardless of their surroundings.
3. Avoidance of apoptosis (programmed cell death). Cells have the ability to ‘self-destruct’; a process known as apoptosis. This is essential for tissue maintenance. Cancer cells, even though grossly abnormal but still not activate apoptosis.
4. Limitless replicative potential. Cancer cells are capable of infinite growth and replication unlike normal cells which die after a certain number of divisions. These “immortal” cells have damaged chromosomes which bypass the division limit barrier and never obtain senescence.
5. Promoting blood vessel construction or sustained angiogenesis. Angiogenesis is the formation of blood vessels. Cancer cells, on their own, can trigger the formation of secluded blood vessels for their nourishment. Due to the haphazard cell cycle of cancer cells, they require more oxygen and nutrients.
6. Tissue invasion and metastases formation. Cancer cells can break away from their regions of origin to invade surrounding tissue and metastasize (spread) to distant body parts. This is the dictating factor as to whether a tumor is malignant or benign.
Causes of Cancer
A carcinogen is any substance that promotes carcinogenesis, the formation of cancer. Cancer is the result of mutation of an individual’s genes or simply, the interaction between a person’s genetic factors and three main categories of external agents, including:
1. Physical carcinogens; such as ultraviolet rays and ionizing radiation.
2. Chemical carcinogens; such as asbestos, tobacco smoke and various food and water contaminants such as; aflatoxin and arsenic.
3. Biological carcinogens. This may be inborn (hereditary) or as a result of infections from certain viruses, bacteria or parasites.
Other risk factors for cancers include alcohol use; physical inactivity or lack of exercise, age, gender (prostate cancer only affects males, and uterine cancer only affects females), racial or ethnic origins, air pollution, presence of chronic infections such as; ulcers, HIV, HPV, Hepatitis B and C.
Signs and Symptoms
Initially, cancer produces no symptoms. Signs and symptoms appear as the mass grows or ulcerates. Cancer is very difficult to diagnose, thus giving it the pseudonym, “the great imitator”. Both local and systemic symptoms occur in cancer patients. Local symptoms are often as a result of the mass of the tumor or its ulceration. For instance; colorectal cancer (cancer of the rectum and/or colon) may lead to blockages in the bowel, lung cancer may also lead to blockage of the bronchus resulting in acute pneumonia. Systemic symptoms however are the same for all cancer patients regardless of the type of cancer. They include; unintentional weight loss, fatigue, altered mental state, frequent dehydration, constipation, headaches and seizures. Metastasis is common in most malignant tumors and occurs in the late stages of cancer. It is the spread of cancer to other locations in the body via the lymphatic system or the circulatory system or both. Cancers usually metastases to the lungs, bones, liver and the brain. Most cancer deaths are as a result of metastasized cancers.
Types of Cancer
Cancer can exist almost everywhere on the human body and there are over a hundred types of cancers. Annually, there are approximately 17 million new cases of cancer worldwide. Below are the most common types of cancers worldwide, the number of new cases diagnosed annually and their percentages.
Global Cancer Incidence :both sexes
Stages or Grades of Cancer
The stage of a cancer generally describes the size of a tumor and how far it has progressed from where it originated.
1. Stage 0: The cancerous cells are located in the region where they started (in situ) and haven’t spread yet.
2. Stage 1: The cancer is small and its growth and division is still minimal. Cancer is still in situ.
3. Stage 2: The cancer is grown and developed, but hasn’t spread yet
4. Stage 3: The cancer is large and may have spread to the surrounding tissues via the cardiovascular or lymphatic system.
5. Stage 4: The cancer is confirmed to have spread from where its origin site and has colonized at least one other body organ. Cancer in this stage is then said to have progressed to metastatic cancer.
Treatment and Management
Modern oncology has proven that numerous treatment options for cancer exists. The primary ones include; surgery, chemotherapy, radiation therapy, hormonal therapy, gene therapy, targeted therapy and palliative care. The form of treatments used depends on the type, location and grade of the cancer as well as the patient’s health and preferences.
1. Chemotherapy: Chemotherapy is a type of cancer treatment that uses drugs to kill cancer cells.
2. Hormone therapy: Hormone therapy is a treatment that slows or stops the growth and division of the various cancer types that uses hormones to grow (i.e. breast and prostate cancers)
3. Immunotherapy: A type of cancer treatment in which your immune system is aided to fight cancer.
4. Radiation therapy: High doses of radiation to shrink and kill malignant tumors.
5. Surgery: A procedure in which a surgeon removes a cancerous tumor from the body.
6. Stem cell transplant: A procedure which entails the restoration of blood-forming stem cells in cancer patients.
7. Targeted therapy: This is a highly specific technique used in cancer treatment that targets the changes in cancer cells that help them grow, divide and spread.
One must note however that cancer does not only occur in humans but can also be found on animals such as dogs, cats, rodents and many others. In non-human subjects of cancer, most especially dogs, a few types of transmissible cancer have been described, wherein cancer spreads between organisms.
Just remember; eat healthy, avoid drug abuse, exercise regularly, avoid stigma towards cancer patients and visit health centers regularly because early detection is key. Cancer is not the end.
1. Cancer Treatments. Modern Oncology. Retrieved from https://www.cancer.gov/about-cancer/treatment/types
2. Types of Cancer. Global Cancer Incidence. Retrieved from https://www.who.int/news-room/fact-sheets/detail/cancer
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