“I thought I was not old enough to have cancer!” So said this 40-year-old mother of four who had presented with a three-year history of a self-discovered lump in her breast as I disclosed the diagnosis of breast cancer to her.
The sentiment expressed by this lady is widespread among the general population and health care professionals in Africa. This is based on health information and professional education that has presented cancer as a disease of “old people.” This assumption belies the facts. Over the last decade, in my practice in Africa, a quarter of my patients with breast cancer were aged 38 years or less, while 75% were age 55 years and below. In fact only 10% of my patients were older than 60 years of age. This pattern of age of patients at clinical presentation is similar across Africa with only minor variations. Why is this? What should we do about it?
Generations of African clinicians were taught that cancers were a “rare” disease that occurred among the old. Most of the standard clinical textbooks used in medical schools in Africa were written in developed countries with description of cancers based on the epidemiology and clinical presentation in those environments. With a high life expectancy, most patients presenting with cancer in the West indeed are old (except for the well-known pediatric cancer cases of course). In contrast, in Africa, with its relatively younger population, most of the cancer patients that clinicians see are young. This is of course because the populations from where these patients were derived are young and nothing more.
Limited understanding of measures of disease occurrence also affects understanding of the pattern of cancer in many African countries. To illustrate, consider an idealized African country with a female population of 100 million. About 50 million of these will be aged 20 years and below (see the U.S. Census Bureau for Population Pyramids of different countries and check out an animation of the African population pyramid; 45 million will be aged between 20 and 60; and 5 million older than 60 years of age.
Assuming incidence of cancer among women between 20 and 60 in this population is 20 per 100,000, this translates to 9,000 new cancer cases per year. Assume further that the incidence of cancer among those older than 60 is twice this, that is 40 per 100,000, this translates to 2,000 cancer cases per year. In total, there are 11,000 new cancer cases but most of them occur in people within the 20 to 60 age bracket. A hospital based case series which manages to capture all these patients will report that “only 18% of cancers occurring in this environment occur among people older than 60 years of age in contrast to reports from Western studies.” While this is true, the implied interpretation that cancer incidence is higher among the young in this population is however false.
This picture is further distorted by other factors. Because cancer is a chronic disease, the differential contribution to the prevalence pool by the young differs from the old. The older cancer patient is at risk of death from other co-morbidities (competing risk) so old cancer patients do not persist long in the measurable prevalence pool. Other factors—socio-economic status, education, health belief models, access to health care, health systems navigation, cultural, economic and psychological factors—also conspire to impede access of the old and elderly to hospital care for any disease in Africa and for cancer care in particular. Hospital case series therefore under-report the prevalence of the disease in this population. Though the incidence (number of new cases per population per unit time) of cancer is higher in the older population, the prevalence (number of all instances of an event in a population [new and old] per unit time) is more in the younger population.
So what does this mean to the general population and clinicians in Africa? Clinicians need to be aware that because of the structure of their populations, most of the patients with cancer that we will see will be young and middle aged. Thus messages on cancer awareness should be designed for this target population. They need to teach their students about this pattern of disease and the reason behind it. They should also interpret data on cancer incidence and its biological implications in Africa with care.