To begin with, it’s pertinent to put cancers in the right perspective. By way of definition, a cancer is a malignant tumour or swelling composed of abnormal cells capable of undergoing uncontrolled proliferation. Many erroneously hold the view that every swelling or lump is a cancer. However, this is not so. Unlike benign swellings, cancerous cells generally have the tendency to invade surrounding tissues and sometimes metastasize (break off and spread) to distant body tissues via the bloodstream or lymphatic system. Cancers result when there is a disruption to the normal process of cell division. Body cells are continuously undergoing cell division, albeit in a controlled manner to replace aging and dead cells. However, a fault or mutation sometimes occurs during this process. If not promptly repaired by the body, this results in the formation of abnormal cells which continue to proliferate uncontrollably and ultimately lead to cancer.
Arguably, the health burden of cancer is enormous. Cancer is said to kill more people annually than HIV/AIDS, Malaria and Tuberculosis. According to the International Agency for Research on Cancer (IARC), by 2030, more than 21 million new cases of cancer would have been diagnosed with 13 million people dying from cancer every year. Furthermore, statistics have revealed that 80000 Nigerian women die from various forms of cancer every year with breast cancer at the top of the list.
A complex interplay of several risk factors, some of which are discussed below determines who comes down with cancer and who does not:
Cigarette smoking, active or passive is implicated in most cancers including lung, nasopharyngeal, oesophageal and prostate cancers to mention a few. In fact, research has shown that about 33% of all annual cancer deaths in the United States result from smoking. Approximately 98% of patients with Small Cell Lung Cancer (SCLC) have a significant smoking history and fortunately, cessation of smoking has been correlated with improved survival in these patients.
Compared with people of normal weight and Body Mass Index (BMI), obese individuals stand a greater risk of some cancer types including cancers of the pancreas, colon, kidneys, oesophagus, breast and the endometrium among others. One explanation that has been proposed for this increased risk is that fat tissues produce excessive quantities of oestrogen in obese people. High oestrogen levels have been associated with increased risk of breast and endometrial cancers. Furthermore, obese individuals are more likely to have elevated blood levels of insulin and Insulin-like Growth Factor 1 (IGF-1) which favour the development of some cancers. Studies have shown that overweight and obese individuals stand 200-400% higher risk of endometrial cancer than their counterparts with a normal BMI.
Immunodeficient individuals such as people living with HIV/AIDS are at more risk of developing certain types of cancer. Three of these cancers namely Kaposi Sarcoma, Non-Hodgkin Lymphoma and Cervical Cancer are referred to as AIDS-defining illnesses. For instance, an individual infected with HIV has several thousands higher risk of manifesting Kaposi Sarcoma and 70 times higher risk of developing Non-Hodgkin Lymphoma. Some other cancer types they are at risk of include anal cancer, Hodgkin lymphoma and lung cancer. Because HIV/AIDS weakens the immune system, it is believed that it predisposes to some other infections that can cause cancer e.g Human Papilloma Virus (HPV) infection that has been implicated in cervical cancer.
Excessive Alcohol Intake
Studies have shown that excessive consumption of alcohol increases your risk of oral, throat, oesophageal and liver cancer. Consequently, if you quit excess drinking, your risk of these deadly cancers will be significantly less.
Excessive exposure to Sunlight
Individuals that expose themselves to intense sunlight inadvertently increase their risk of skin cancers. Numerous studies have implicated Ultraviolet (UV) radiation in the pathology of skin cancers, including melanoma. Melanin is a natural skin pigment that offers significant protection from ultraviolet rays. This is why light-skinned people who have less melanin pigment in their skin are more likely to experience sunburn and skin cancer.
Positive Family History
For most cancers, individuals who have one or more close relatives (especially first-degree relatives) that have been diagnosed with such cancers have a significantly higher risk. Such people are said to be genetically predisposed because they may have inherited some of the abnormal genes. For instance, a family history of breast cancer in a first-degree relative is one of the important risk factors for this cancer. If a mother or sister is affected by breast cancer, the lifetime risk of developing the disease is increased by four folds.
As people increase in age, their risk of developing most cancers also tends to increase. For example, while breast cancer is very rare in women below 25 years, the incidence reaches a plateau in women aged 50-55 years. Furthermore, prostate cancer is a disease condition that is typically seen in the elderly (Age >65 years) and the prevalence can be as high as 80% at 80 years of age.