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HEPATOCELLULAR CARCINOMA IN SUB-SAHARAN AFRICA
By Michael Charles Kew
Trafford PublishingCopyright © 2012 Michael Charles Kew
All right reserved.
Africa is the second largest of the world's continents. It covers 30,300,000 square kilometers, approximately one-fifth of the global land area. The continent is sparsely inhabited, with a population of some 800 million people accounting for only 12% of the global population. Most of Africa's population lives to the south of the Sahara desert, where the vast majority of the inhabitants are Blacks. North Africa, in climate, customs, and cultural background, is Mediterranean rather than African, and almost every distinctive feature of cancer in Africa belongs to sub-Saharan Africa [Parkin et al, 2003]. None more so than hepatocellular carcinoma.
The global cancer burden has been, and will continue to be, increasingly influenced by the growth and aging of the world's population. In the year 2000, 10.1 million new cases of cancer were recorded worldwide, and this figure is expected to increase to 15 million by the year 2020 [Stewart and Kleihues, 2003]. Furthermore, by the year 2030 an annual total of 27 million new cases of cancer, 17 million deaths attributed to cancer, and 75 million people living with cancer could be expected [Boyle, 2006]. The impact of this increase will be felt in all geographical regions, but especially in the economically-constrained (low income; developing) regions, including sub-Saharan Africa.
To date, information on the occurrence of hepatocellular carcinoma in sub-Saharan Africa, in common with that on all cancers in the sub-continent, has been neither complete nor always accurate, as anyone who has ever tried to obtain accurate estimates of cancer incidences in the sub-continent will attest [Berman, 1951; Oettlé, 1964; Cook and Burkitt, 1971; Parkin et al, 2003]. As a result, the true incidence of hepatocellular carcinoma in sub-Saharan Africa has been significantly understated. Knowledge of cancer incidence and patterns in the African sub-continent has, until quite recently, been based largely on the work of a few pioneering clinicians and pathologists, who described series of cancer patients seen in their practices in terms of age, sex, cancer site, and histology [Berman, 1951; Oettlé, 1964; Cook and Burkitt, 1971]. Comparisons based on relative frequencies of different cancers in such case series may be misleading [Parkin et al, 2003]. Because biopsies and necropsies were, and to a lesser extent still are, seldom performed in Black African patients thought to be suffering from hepatocellular carcinoma, estimates of the occurrence of the tumor in the sub-continent, but particularly in rural areas where 80% of the Black population lives, under-estimate the true incidence of the tumor. Medical facilities in these rural areas are few and far between, and it has long been known that attendance at the local hospital decreases with its distance from the patient's home [Davies et al, 1965]. Furthermore, in the past, hepatocellular carcinoma has been, and even now is, often diagnosed solely on the basis of compatible clinical features, supported in some patients by either a raised serum -fetoprotein concentration or the finding of a mass-lesion in the liver on first-line ultrasonographic imaging of the liver [Kew, 2007]. The more sophisticated and expensive dynamic hepatic imaging techniques that today enable a firm diagnosis of hepatocellular carcinoma to be made on the basis of the early hypervascularity of the tumor followed by rapid wash-out of the indicator from the tumor are available in a few medical centers only in the large cities in sub-Saharan Africa, and certainly not in the rural areas.
Reports on hospital-based series of patients with hepatocellular carcinoma in the African sub-continent have been, and remain, biased by the interests and competence of the local clinicians, the diagnostic facilities and therapeutic options available, and the accuracy and completeness of record keeping [Oettlé, 1964; Parkin et al, 2003]. These short-comings are compounded by the nihilistic attitude of many doctors in sub-Saharan Africa to making a definitive diagnosis of hepatocellular carcinoma, which is engendered by the extremely poor results of treatment of this tumor and the dismal prognosis of the patients [Kew, 2007].
The appropriate statistic for comparing cancer risks between populations is the incidence rate [Parkin et al, 2003]. Incidence rates should be derived from population-based cancer registries, which aim to record information on all new cases of cancer that occur in a defined population [Parkin et al, 2003]. Accurate registration depends upon identifying every case of the cancer, which can only be achieved if patients have ready access to appropriate health services. When the necessary resources are inadequate, the number of patients with access to these services is limited and meaningful cancer registration is unlikely to be achieved [Oettlé, 1964; Parkin et al, 2003].
Another difficulty is to correctly identify the place of residence of cancer patients, so that when incidence rates are calculated, only those cases belonging to the population at risk are included [Flegg Mitchell, 1966; Parkin et al, 2003]. Unfortunately, place of residence is not an obvious concept in some sub-Saharan African regions. This is especially true in eastern and southern Africa, where Blacks living and working in urban areas often retain a foothold in their home village, to which they return intermittently on vacation. They may also return home to seek medical advice or care from the local traditional healers (witch-doctors; 'nyangas'), or, when seriously ill or very old, to die [Flegg Mitchell, 1966]. Consequently, they may not be included in either an urban-based or a rural-based cancer registry. Moreover, many Black Africans living permanently in rural areas rely on the diagnostic and treatment services of traditional healers rather than conventional doctors [Flegg Mitchell, 1966] and they too would not be included in rural-based cancer registries. On the other hand, some Black men and women living in rural areas travel to towns or cities to stay with a relative when they are ill and need to visit a hospital. The address given to the hospital will be that of the urban relative. The few cancer registries in sub-Saharan Africa are almost all based in urban centers where diagnostic and treatment facilities are available. In compiling these cancer registries accurately the main technical problem is to avoid registration of these 'temporary' residents migrating into the urban area for short-term treatment or other reasons [Flegg Mitchell, 1966].
Compounding these difficulties, may be a low standard of literacy of the rural African population [Flegg Mitchell, 1966].
In order to be able to study time trends in the occurrence of a tumor it is important that the degree of completeness of registration of incident cancer cases should be constant throughout the period under consideration [Wabinga et al, 2000]. This has not always been the case in the few such studies performed in sub-Saharan Africa.
Without a comprehensive and accurate population survey, it is not possible to ascertain the true incidence of hepatocellular carcinoma in a rural Black African population, and one can only guess at how well the profile obtained from urban areas reflects that of the population as a whole [Friis and Storm, 1993].
A further difficulty in recording accurate information about the incidence of hepatocellular carcinoma in sub-Saharan Africa is the lack of appropriately trained personnel [Parkin et al, 2003]. There has been and continues to be a shortage, not only of epidemiologists and statisticians to plan and execute the collection of data in a processable form, but also of suitably trained personnel to man the registry infrastructure. Moreover, health ministries in most sub-Saharan African countries, when apportioning their limited financial and other resources, have regarded cancer as a lower public health priority than infectious and nutritional diseases [Parkin et al, 2003]. As a result, adequate governmental funds have not been, and continue not to be, made available for the institution and running of cancer registries.
With regard to mortality data, the information available in sub-Saharan Africa is even more questionable than that for incidence. Death registration and certification of cause of death are neither feasible nor a statutory requirement in virtually all countries in the sub-continent [Parkin et al, 2003].
As a result of these hurdles and shortcomings, the history of cancer registration in sub-Saharan Africa from the time that the earliest registries were instituted in the 1950s has been disappointing. Even today, a minority of countries have reliable cancer registries and, with few exceptions, these registries are based in urban settings. The first country-wide cancer registry with substantial rural coverage was established as recently as 1988 [Bah et al; 1990]. Moreover, these deficiencies have been compounded by the infrequency and unreliability of population censuses in the African subcontinent [Parkin et al, 2003].
Accurate knowledge of the epidemiological data concerning hepatocellular carcinoma will be required to play a role in guiding future treatment and ultimately strategies for the prevention of the tumor in sub-Saharan countries.
Despite the under-diagnosis and under-reporting of hepatocellular carcinoma in the African sub-continent, it is manifestly evident from the information available that the tumor occurs commonly and is a major cause of cancer deaths in Black African peoples living in sub-Saharan Africa.
INCIDENCE OF HEPATOCELLULAR CARCINOMA
Allowing for the limitations in ascertaining the true incidence of hepatocellular carcinoma in the indigenous populations of sub-Saharan Africa, the information available should be considered in perspective with the global incidence of the tumor.
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