Analyses of cancer incidence in black gold miners from Southern Africa (1964-79)

Decrease in liver cancer incidence rates in Bamako, Mali over 28 years of population-based cancer registration (1987-2015)

BACKGROUND

Primary liver cancer is common in West Africa due to endemic risk factors. However, epidemiological studies of the global burden and trends of liver cancer are limited. We report changes in trends of the incidence of liver cancer over a period of 28 years using the population-based cancer registry of Bamako, Mali.

AIM

To assess the trends and patterns of liver cancer by gender and age groups by analyzing the cancer registration data accumulated over 28 years (1987-2015) of activity of the population-based registry of the Bamako district.

METHODS

Data obtained since the inception of the registry in 1987 through 2015 were stratified into three periods (1987-1996, 1997-2006, and 2007-2015). Age-standardized rates were estimated by direct standardization using the world population. Incidence rate ratios and the corresponding 95% confidence intervals (CI) were estimated using the early period as the reference (1987-1996). Joinpoint regression models were used to assess the annual percentage change and highlight trends over the entire period (from 1987 to 2015).

RESULTS

Among males, the age-standardized incidence rates significantly decreased from 19.41 (1987-1996) to 13.12 (1997-2006) to 8.15 (2007-2015) per 10⁵ person-years. The incidence rate ratio over 28 years was 0.42 (95%CI: 0.34-0.50), and the annual percentage change was -4.59 [95%CI: (-6.4)-(-2.7)]. Among females, rates dropped continuously from 7.02 (1987-1996) to 2.57 (2007-2015) per 10⁵ person-years, with an incidence rate ratio of 0.37 (95%CI: 0.28-0.45) and an annual percentage change of -5.63 [95%CI: (-8.9)-(-2.3)].

CONCLUSION

The population-based registration showed that the incidence of primary liver cancer has steadily decreased in the Bamako district over 28 years. This trend does not appear to result from biases or changes in registration practices. This is the first report of such a decrease in an area of high incidence of liver cancer in Africa. This decrease may be explained by the changes and diversity of diet that could reduce exposure to aflatoxins through dietary contamination in this population.

Hepatocellular carcinoma: Clinical-pathological features and HIV infection in Mozambican patients<sup/>

BACKGROUND AND AIMS

Mozambique had been ranked among the countries with the highest global incidence of HCC with chronic hepatitis B infection and high exposure to aflatoxin-B1 (AFB1) being major risk factors. Indeed, HCC remains one of the most frequent cancer in Maputo. On the other hand, Mozambique has a high prevalence of infection with Human Immunodeficiency virus (HIV). Our study aims to describe the epidemiology, clinicopathological and serological features of patients with HCC in Maputo Central Hospital and its relationship with HIV.

METHODS

A series of 206 patients, diagnosed with HCC via fine needle aspiration, were consecutively included in the study. Patient data was collected using a questionnaire and all patients were tested for HBV, HCV, HIV.

RESULTS

Median age was 49 years old and the M: F sex ratio was 2.4. A total of 114 (56.2%) of the patients were HBsAg positive. Hepatitis C antibodies were present in 8.9% of cases, and co-infection with HBV and HCV (HBsAg/anti-HCV) was observed in 4 (2.0%) cases. The remainder, 36.3%, were neither hepatitis B- nor C-related. HIV was detected in 34 cases (18.0%) cases. HIV-HBV or HIV-HCV co-infections were observed in 22 (68.8%) and 2 (6.2%) cases. Overall, positivity for HIV was associated with younger age, and especially in patients with HBsAg+/anti-HCV+.

CONCLUSIONS

Our data emphasize the need for a reinforcement of secondary prevention measures in Mozambique. Serological screening for HBV in people born before universal anti-hepatitis B immunization (2001), effective screening, and specific management in HIV(+) patients are urgently needed.

Changes in the geographical and temporal patterns of cancer incidence among black gold miners working in South Africa, 1964-1996

We describe here the results of the final 8 years of geographical and temporal data of a 33-year study of the cancer experience of 12.8 million man-years of black miners working on the gold fields of South Africa over the period 1964-96. These workers were recruited from 15 territories, the major areas during the most recent period being Lesotho (26.8%), Transkei (21.5%) and Mozambique (15%). The earliest analyses, 1964-71 and 1972-79, showed hepatocellular and oesophageal cancers to be the most frequent cancers. The final analysis, for 1989-96, however, shows marked temporal changes in the relative position of four cancers or grouped malignancies: respiratory cancer up by 236%, hepatocellular carcinoma down to 32%, oesophageal holding steady, and lymphatic system cancers up by 420%, almost certainly because of association with HIV/AIDS infection. Significant geographical variations occurring between the home areas of the miners are important, as mining operations have little to do with the cancers that develop. The causes are essentially socio-environmental rather than occupational, and this means that the rates of the major cancers in the miners are surrogate measures of the same cancers in the home areas.

Heavy metals in soil, vegetables and fruits in the endemic upper gastrointestinal cancer region of Turkey

The environmental exposure to heavy metals is a well-known risk factor for cancer. We investigated levels of seven different heavy metals, (Co, Cd, Pb, Zn, Mn, Ni and Cu) in soil, fruit and vegetable samples of Van region in Eastern Turkey where upper gastrointestinal (GI) cancers are endemic. Heavy metal contents of the samples were determined by flame atomic absorption spectrometer. Four heavy metals (Cd, Pb, Cu and Co) were present in 2- to 50-fold higher concentrations whereas zinc levels were present in 40-fold lower concentrations in soil. The fruit and vegetable samples were found to contain 3.5- to 340-fold higher amounts of the six heavy metals (Co, Cd, Pb, Mn, Ni and Cu) tested. The volcanic soil, fruit and vegetable samples contain potentially carcinogenic heavy metals in such a high levels that these elements could be related to the high prevalence of upper GI cancer rates in Van region.

A population at high risk for esophageal cancer in the north-east of Italy

Esophageal cancer is generally characterised by relatively low incidence and mortality rates in Europe. However, a high-risk population for this tumour is resident in the north-east of Italy. Several studies have been conducted on this population of males confirming the major role of alcohol and tobacco consumption alone and in combination. The inhabitants of this area of Italy constitute an ideal target population for studies of molecular epidemiology aimed at elucidating the natural history of the disease which is still ill-defined, and the distribution of genetic alterations at a population level.

[Geography of cancer of the esophagus]

A review of available data on the epidemiology of oesophageal cancer from different parts of the world as well as an analysis of new findings, suggests the following conclusions: 1. A peculiar incidence pattern of the disease exists worldwide with roughly 500-fold differences in rates (truncated) between the highest and lowest risk areas. 2. Males are generally affected more than females, with a few exceptions such as the very high risk regions of northern Iran. The highest male: female sex ratios (based on truncated incidence rates) have been reported from Normandy and Brittany (25:1) and the lowest ratios from South Gorgan in northern Iran (0.5:1). 3. There is evidence that the frequency of oesophageal cancer is rising over time in many regions, particularly among the black population of the United States and in England and France. 4. Most of the areas reflecting a very high incidence of this disease are located in poorer parts of the world. 5. The frequency of this disease varies among the native and migrated population in different countries.

Aflatoxin exposure, hepatitis B virus infection and liver cancer in Swaziland

A study was carried out in Swaziland to assess the relationship between aflatoxin exposure, hepatitis B infection, and the incidence of liver-cell carcinoma, which is the most commonly occurring malignancy among males in Swaziland. Levels of aflatoxin intake were evaluated in dietary samples from households across the country, and crop samples taken from representative farms. Prevalence of hepatitis B markers was estimated from the serum of blood donors, and liver cancer incidence was recorded for the years 1979-83 through a national system of cancer registration. Across 4 broad geographic regions, there was a more than 5-fold variation in the estimated daily intake of aflatoxin, ranging from 3.1 to 17.5 micrograms. The proportion of HBV-exposed individuals was very high (86% in men), but varied relatively little by geographic region; the prevalence of carriers of the surface antigen was 23% in men, and varied from 21 to 28%. Liver cancer incidence varied over a 5-fold range, and was strongly associated with estimated levels of aflatoxin. In an analysis involving 10 smaller subregions, aflatoxin exposure emerged as a more important determinant of the variation in liver cancer incidence than the prevalence of hepatitis infection. Aflatoxin estimates from crop samples appeared to be a reasonable surrogate for dietary measurements. A comparison with dietary aflatoxin levels measured in an earlier survey in Swaziland suggested that programmes aimed at reducing contamination levels had had some success.

Inhibition of esophageal carcinogenesis in corn-fed rats by riboflavin, nicotinic acid, selenium, molybdenum, zinc, and magnesium

The effect of individual vitamins and minerals on esophageal carcinogenesis was assessed by supplementing a diet (based on corn) that was marginally deficient in many micronutrients. The test diets were fed to weanling inbred BD IX rats for 45 days; they were then given five subcutaneous doses (3 mg/kg body wt) N-nitrosomethylbenzylamine (MBN) over two and one-half weeks. The diets were continued until termination: 150 days later; at that time all rats were still clinically normal. Marked reductions in the number of tumors and tumor-bearing rats were recorded in groups of rats given supplements of riboflavin, nicotinic acid, zinc, magnesium, selenium, and molybdenum. Various combinations of nutrients did not distinctly reduce the tumor yield further; however, tissue analyses suggest that individual supplements could enhance the status of other marginally deficient nutrients. When the experiment was repeated, but was varied by commencing the supplements only well after the cessation of MBN exposure, inhibitory effects on tumorigenesis were still exerted by most nutrients. We emphasized that these nutritional effects along with the epidemiological evidence in humans are relevant to early prevention; also, the treatment of premalignant esophageal changes by high doses of these nutrients may be unwise. The merits of food supplementation schemes are discussed.

Lung cancer 1978-1981 in the black peoples of South Africa

Mortality data on lung cancer among the black populations of South Africa, newly available from the first ever nation-wide enumerations, are analysed for age-specific rates and significant geographical and intertribal variations. This study finds a higher incidence at younger ages than among whites, an urban excess similar to other population groups in South Africa and a higher incidence among the Xhosa than Zulu. It is suggested that an anti-smoking campaign is urgently required among blacks in South Africa.

Hepatocellular carcinoma and dietary aflatoxin in Mozambique and Transkei

Estimations of the incidence of hepatocellular carcinoma (HCC) for the period 1968-74 in the Province of Inhambane, Mozambique, have been calculated and together with rates observed in South Africa among mineworkers from the same Province indicate very high levels of incidence in certain districts of Inhambane. Exceptionally high incidence levels in adolescents and young adults are not sustained at older ages and suggest the existence of a subgroup of highly susceptible individuals. A sharp decline in incidence occurred during the period of study. Concurrently with the studies of incidence, 2183 samples of prepared food were randomly collected from 6 districts of Inhambane as well as from Manhica-Magude, a region of lower HCC incidence to the south. A further 623 samples were taken during 1976-77 in Transkei, much further south, where an even lower incidence had been recorded. The mean aflatoxin dietary intake values for the regions studied were significantly related to HCC rates. Furthermore, data on aflatoxin B1 contamination of prepared food from 5 different countries showed overall a highly significant relationship with crude HCC rates. In view of the evidence that chronic hepatitis B virus (HBV) infection may be a prerequisite for the development of virtually all cases of HCC and given the merely moderate prevalence of carrier status that has been observed in some high incidence regions, it is likely that an interaction between HBV and aflatoxin is responsible for the exceptionally high rates evident in parts of Africa and Asia. Various indications from Mozambique suggest that aflatoxin may have a late stage effect on the development of HCC. This points to avenues for intervention that could be more rapidly implemented than with vaccination alone.

Oesophageal cancer in Zulu men, South Africa: a case-control study

The high rate of oesophageal cancer amongst southern African blacks has also been recorded amongst the Zulus. Data embracing a wide spectrum of factors pertaining to socio-economic status, nutrition, exposure to carcinogens, tobacco and alcohol usage and traditional health practices were obtained from 211 hospitalized oesophageal cancer patients and compared with hospital population controls matched for age and urban-rural background. Stepwise logistic regression analysis with adjustment for age effects showed that four of the many factors could adequately model the odds of being a cancer case. They were the daily consumption of purchased maize meal (relative risk (RR) 5.7) currently smoking commercial cigarettes (RR 2.6), pipe smoking (RR 2.1), and a reduction of risk in those using butter or margarine daily (RR 0.51). Further significant differences (P less than 0.05) in 12 other factors suggest that those with rural assets but an ability to earn a modest income external to the subsistence economy are at highest risk. They represent a transitional state of Westernisation which is characterised by excessive smoking habits and a diet having a low vitamin and mineral density. These results provide further evidence for the need to combat smoking and for a program of nutrient enrichment of maize meal.

Eleven sites of cancer in black gold miners from Southern Africa: a geographic enquiry

The 5-year study of cancer in black gold miners, 1964-68, previously reported (Robertson et al., 1971) has now been extended for a separate 8-year period, 1972-79. This allows analyses of all cancers together and of 6 less common sites of cancer severally: lymphosarcomas, colon and rectum, leukaemia, stomach, pancreas and buccal cavity and also of those too rare to classify. The malignancies are considered by territory of origin of the gold miners. Lesotho miners have significantly fewer (P less than 0.05) tumours of the lymphatic and haemopoietic tissues and Natal miners have the highest incidence rates for 5 of the 6 sites (excluding leukaemia). A simple grouping method is applied to determine which of the 11 sites of cancer in the miners have similar distributions in their 10 territories of origin. The aetiological implications of clusters over space of certain sites of cancer are discussed. Finally, temporal change over the years 1964-79 shows a significant decrease overall (P less than 0.01) in cases of lymphosarcomas and colo-rectal cancers and an increase (P less than 0.05) in stomach cancer. The rare tumour, Kaposi's sarcoma, has also decreased significantly between the 2 periods studied.