Generally, the causes of cancer are multifactorial and often difficult to ascribe a single etiology in a particular patient. The most common causes of cancer are environmental insults (90-95%). Genetic factors account for 5-10% of cancers. Irrespective of the cause, the final pathway is disruption of the normal cell cycle leading to uncontrolled proliferation of cells.
The following are some of the etiologies of cancer:
- Age – cancer can occur at any age. But, the type and behavior of cancer is different between children and adults. The chance of getting the most common adult cancers increases with increasing age.
- Sex – sex is another discriminating factor. For example, breast cancer is 150-200X more common in females than in males. On the other hand, stomach cancer is 2-5X more common in males than in females.
- Tobacco – globally, there are an estimated 1.3 billion smokers smoking more than 15 billion cigarette daily. Men smoke 5X the rate of women. Cigarette smoking is estimated to cause more than 1 million cancer deaths annually worldwide. Apart from Lung cancer, numerous international prospective epidemiologic studies and case-control studies involving millions of subjects repeatedly confirmed the causal link between smoking (of any form) and cancers.
The main known addictive agent in cigarette smoke, nicotine, is not carcinogenic. Rather, there are thousands of harmful chemicals and carcinogens like polycyclic aromatic hydrocarbons (PAH). Cigarette smoking is the greatest preventable cause of cancer and represents the largest known voluntary exposure to multiple carcinogens. It is also a major regulatory failure as smoking has been directly or indirectly promoted. However, in recent years, after understanding these grave consequences, countries are working hard to reduce smokers. However, these efforts are far from success in most low and middle income countries. According to WHO (2015), 8.9% of Ethiopian men and 0.5% Ethiopian women age 15 years or older smoke tobacco products. Recently, Ethiopian parliament unanimously approved one of Africa’s anti-tobacco law which requires banning to sell to people under the age of 21, 100% smoke free public and work places, bans tobacco advertizing and promotions, restricts the sale of flavored tobacco products and mandates pictorial warning labels covering 70% of the front and back of all tobacco products.
- Chemicals – e.g., asbestos, aflatoxin, Alcohol, benzene, cadmium, arsenic
- Obesity
- Diet rich in animal products and low in fruits and vegetables
- Physical Inactivity – nowadays it has been called “the new smoking”
- Viral infections and some of the resulting cancers include the following;- HBV and HCV – Hepatocellular Cancer, EBV – Lymphoma, Nasopharyngeal cancer, gastric cancer, HSV 8 (KSHV) – Kaposi sarcoma, HTLV 1 – Adult T-cell leukemia/lymphoma, HPV 16 and 18 – Anogenital (perianal, anal, Cervical and Vulvar) and Oropharyngeal cancers, HIV – causes immunodeficiency and increases the risk of cancer
- Radiations exposure
- Ultraviolet B
- Cosmic rays (at high altitudes)
- Medical procedures (diagnostic and therapeutic)
- Disasters from nuclear plants and use of nuclear weapons (e.g., Chernobyl nuclear accident on April 26, 1986 and nuclear bomb dropped to Hiroshima and Nagasaki during WWII in 1945)
Source: drabduadem.com/en