D. M. Parkin

Estimates of the world‐wide prevalence of cancer for 25 sites in the adult population

In health services planning, in addition to the basic measures of disease occurrence incidence and mortality, other indexes expressing the demand of care are also required to develop strategies for service provision. One of these is prevalence of the disease, which measures the absolute number, and relative proportion in the population, of individuals affected by the disease and that require some form of medical attention. For most cancer sites, cases surviving 5 years from diagnosis experience thereafter the same survival as the general population, so most of the workload is therefore due to medical acts within these first 5 years. This article reports world‐wide estimates of 1‐, 2–3‐ and 4–5‐year point prevalence in 1990 in the population aged 15 years or over, and hence describes the number of cancer cases diagnosed between 1986 and 1990 who were still alive at the end of 1990. These estimates of prevalence at 1, 2–3 and 4–5 years are applicable to the evaluation of initial treatment, clinical follow‐up and point of cure, respectively, for the majority of cancers. We describe the computational procedure and data sources utilised to obtain these figures and compare them with data published by 2 cancer registries. The highest prevalence of cancer is in North America with 1.5% of the population affected and diagnosed in the previous 5 years (about 0.5% of the population in years 4–5 and 2–3 of follow‐up and 0.4% within the first year of diagnosis). This corresponds to over 3.2 million individuals. Western Europe and Australia and New Zealand show very similar percentages with 1.2% and 1.1% of the population affected (about 3.9 and 0.2 million cases respectively). Japan and Eastern Europe form the next batch with 1.0% and 0.7%, followed by Latin America and the Caribbean (overall prevalence of 0.4%), and all remaining regions are around 0.2%. Cancer prevalence in developed countries is very similar in men and women, 1.1% of the sex‐specific population, while in developing countries the prevalence is some 25% greater in women than men, reflecting a preponderance of cancer sites with poor survival such as liver, oesophagus and stomach in males. The magnitude of disease incidence is the primary determinant of crude prevalence of cases diagnosed within 1 year so that differences by region mainly reflect variation in risk. In the long‐term period however different demographic patterns with long‐life expectancy in high‐income countries determine a higher prevalence in these areas even for relatively uncommon cancer sites such as the cervix.

Cancer incidence and mortality in the European Union: cancer registry data and estimates of national incidence for 1990.

Members of the European Network of Cancer Registries (ENCR) provide population-based data on cancer incidence for some countries and regions of Europe. These were supplemented by estimates in order to provide comparable information on cancer incidence and mortality in the 15 member states of the European Union (EU). The estimated numbers of new cases of cancer (excluding nonmelanoma skin cancer) in 1990 were approximately 706,900 in men and 644,200 in women. Approximately 497,500 men and 398,200 women died of cancer in the same year. The main sites of incident cases in men were lung (21%), large bowel (13%), prostate (12%), bladder (7%) and stomach (7%). For women, the predominant sites were breast (28%), large bowel (15%), lung (6%), uterine corpus (5%) and stomach (5%). The overall incidence rates for males were highest in continental Western Europe (France, The Netherlands, Austria, Luxembourg, Belgium, Germany and Italy) while the rates of Greece, Portugal, Sweden, Ireland, Spain, Finland, the U.K. and Denmark were below the average value for the EC. Rates for females were highest in Northern and Western Europe, with the exception of France, which had a relatively low rate for females, in common with Greece, Spain and Portugal. The geographical variations in incidence of the major cancers are discussed in relation to risk factors. The estimates show the substantial burden of cancer in European Union populations, but there are also indications of effects of past preventive measures and there is scope for further intervention. Cancer registries are an important source of information for cancer control since they provide population-based incidence and survival statistics. These, along with mortality data, are required to obtain a full picture of the frequency of cancer and its effects at the population level. Some 44% of the EU population is covered by registries. The European Network of Cancer Registries aims to standardise the information provided by existing registries and to provide practical assistance to those in development.

Trends in cancer incidence in Kyadondo county, Uganda, 1960-1997.

Incidence rates of different cancers have been calculated for the population of Kyadondo County (Kampala, Uganda) for four time periods (1960–1966; 1967–1971; 1991–1994; 1995–1997), spanning 38 years in total. The period coincides with marked social and lifestyle changes and with the emergence of the AIDS epidemic. Most cancers have increased in incidence over time, the only exceptions being cancers of the bladder and penis. Apart from these, the most common cancers in the early years were cervix, oesophagus and liver; all three have remained common, with the first two showing quite marked increases in incidence, as have cancers of the breast and prostate. These changes have been overshadowed by the dramatic effects of the AIDS epidemic, with Kaposis sarcoma emerging as the most common cancer in both sexes in the 1990s, and a large increase in incidence of squamous cell cancers of the conjunctiva. In the most recent period, there also seems to have been an increase in the incidence of non-Hodgkin lymphomas. So far, lung cancer remains rare. Cancer control in Uganda, as elsewhere in sub-Saharan Africa, faces a threefold challenge. With little improvement in the incidence of cancers associated with infection and poverty (liver, cervix, oesophagus), it must face the burden of AIDS-associated cancers, while coping with the emergence of cancers associated with Westernization of lifestyles (large bowel, breast and prostate).

Estimation and projection of the national profile of cancer mortality in China: 1991–2005

There are no national-level data on cancer mortality in China since two surveys in 1973–1975 and 1990–1992 (a 10% sample), but ongoing surveillance systems, based on nonrandom selected populations, give an indication as to the trends for major cancers. Based on a log-linear regression model with Poisson errors, the annual rates of change for 10 cancers and all other cancers combined, by age, sex and urban/rural residence were estimated from the data of the surveillance system of the Center for Health Information and Statistics, covering about 10% of the national population. These rates of change were applied to the survey data of 1990–1992 to estimate national mortality in the year 2000, and to make projections for 2005. Mortality rates for all cancers combined, adjusted for age, are predicted to change little between 1991 and 2005 (−0.8% in men and +2.5% in women), but population growth and ageing will result in an increasing number of deaths, from 1.2 to 1.8 million. The largest predicted increases are for the numbers of female breast (+155.4%) and lung cancers (+112.1% in men, +153.5% in women). For these two sites, mortality rates will almost double. Cancer will make an increasing contribution to the burden of diseases in China in the 21st century. The marked increases in risk of cancers of the lung, female breast and large bowel indicate priorities for prevention and control. The increasing trends in young age groups for cancers of the cervix, lung and female breast suggest that their predicted increases may be underestimated, and that more attention should be paid to strategies for their prevention and control.

AIDS-related cancers in Africa: maturation of the epidemic in Uganda.

BACKGROUND The AIDS epidemic has passed its peak in Uganda, with possible consequences for the risk of cancers related to infectious agents. OBJECTIVE To compare the incidence of cancers possibly linked to infections with HIV, before the AIDS epidemic (the 1960s), at its high point (the early 1990s) when HIV-seroprevalence and AIDS notifications peaked, and after the onset of its decline in the later 1990s. METHODS Analysis of incidence rates of infection-associated cancers in the population of Kyadondo county, in 1960-1971, 1991-1994, and 1995-1997. Comparison with data on prevalence of HIV infection, and notifications of AIDS. RESULTS The incidence of Kaposis sarcoma has increased enormously since the 1960s, with a shift to earlier age at onset, and more generalized and nodal disease; there has been little change in the profile during the 1990s. There was a large increase in incidence of squamous cell carcinomas of the conjunctiva, which has continued through the 1990s. Non-Hodgkins lymphomas showed little increase in incidence until the most recent period, in which the incidence has increased both in children (particularly Burkitts lymphomas) and adults. Although the incidence of cervical cancer was higher in the 1990s than the 1960s, it seems doubtful that this is related to HIV infection. Certain other cancers which have been linked to AIDS in western populations (Hodgkins disease, anal carcinoma, childhood leiomyosarcoma) show no changes in risk. CONCLUSION The AIDS epidemic has dramatically changed the profile of cancer in Uganda. Trends in the AIDS-related cancers are consistent with current knowledge concerning the mechanisms behind the increased risk. The incidence of certain cancers with a viral aetiology (liver, cervix, penis, Hodgkins disease) appears not to have been influenced by AIDS.

Cancer incidence in the African population of Harare, Zimbabwe : Second results from the cancer registry 1993-1995

The data of the population‐based cancer registry in Harare, Zimbabwe, for 1993–1995 are presented and compared with those from 1990–1992. The most significant change in rates is the striking increase in the incidence of Kaposis sarcoma (KS) in both men and women, compatible with the evolution of the AIDS epidemic in sub‐Saharan Africa. The incidence of KS doubled in both sexes and now accounts for 31.1% of registered cancers. It has overtaken breast cancer to become the second most common tumour in African women, after cervical cancer, and is now one of the leading childhood tumours, accounting for 10.3% of cancers recorded in children (ages 0–14). With the exception of KS, the incidence and pattern of occurrence of the other malignant neoplasms changed little during the observed 6 years. Int. J. Cancer 85:54–59, 2000.

Outcome of screening by clinical examination of the breast in a trial in the Philippines

The value of screening by Clinical Examination of the Breast (CBE) as a means of reducing mortality from breast cancer (BC) is not established. The issue is relevant, as CBE may be a suitable option for countries in economic transition, where incidence rates are on the increase but limited resources do not permit screening by mammography. Our aims were to assess whether mass screening by CBE carried out by trained para‐medical personnel is feasible in an urban population of a low‐income country, and its efficacy in reducing BC mortality. Our study was designed as a randomised controlled trial of the effect on BC mortality of 5 annual CBE carried out by trained nurses. The target population was women aged 35–64 years, resident in 12 municipalities of the National Capital Region of Manila, Philippines. The units of randomization were the 202 health centres (HC) within the selected municipalities. During 1995 nurses and midwives were recruited and trained in performing CBE. The first round of screening took place in 1996–1997. The intervention however showed a refractory attitude of the population with respect to clinical follow‐up and was discontinued after the completion of the first screening round. Cases of breast cancer occurring in the study population during 1996–1999 were identified by the 2 local population‐based registries. In the single screening round 151,168 women were interviewed and offered CBE, 92% accepted (138,392), 3,479 were detected positive for a lump and referred for diagnosis. Of these only 1220 women (35%) completed diagnostic follow‐up, whereas 42.4% actively refused further investigation even with home visits, and 22.5% were not traced. Of 53 cases that occurred among screen‐positive women in the 2 years after CBE only 34 were diagnosed through the intervention. Eighty cases occurred among screen‐negative women. The test sensitivity for CBE repeated annually was 53.2%. The actual sensitivity of the programme was 25.6% and positive predictive value 1%. Screen‐detected cases were non‐significantly less advanced than the others. Previous studies have shown that most breast cancer cases in the Philippines present at advanced stages and have an unfavourable outcome. Although CBE undertaken by health workers seems to offer a cost‐effective approach to reducing mortality, the sensitivity of the screening programme in the real context was low. Moreover, in this relatively well‐educated population, cultural and logistic barriers to seeking diagnosis and treatment persist and need to be addressed before any screening programme is introduced.

Childhood leukaemia in Europe after Chernobyl: 5 year follow-up

The European Childhood Leukaemia - Lymphoma Incidence Study (ECLIS) is designed to address concerns about a possible increase in the risk of cancer in Europe following the nuclear accident in Chernobyle in 1986. This paper reports results of surveillance of childhood leukaemia in cancer registry populations from 1980 up to the end of 1991. There was a slight increase in the incidence of childhood leukaemia in Europe during this period, but the overall geographical pattern of change bears no relation to estimated exposure to radiation resulting from the accident. We conclude that at this stage of follow-up any changes in incidence consequent upon the Chernobyl accident remain undetectable against the usual background rates. Our results are consistent with current estimates of the leukaemogenic risk of radiation exposure, which, outside the immediate vicinity of the accident, was small.

Aids and cancer in Africa: the evolving epidemic in Zimbabwe.

BACKGROUND Zimbabwe is severely affected by the AIDS epidemic, and many cancers in African populations are related to infectious agents. OBJECTIVE To study the current pattern, and short-term changes in incidence, of cancers related to infectious agents (and especially to HIV), with respect to the evolving epidemic of AIDS. METHODS Analysis of data on the African population of Harare, Zimbabwe, from the Zimbabwe Cancer Registry, for the period 1990-1995. Comparison with data on prevalence of HIV seropositivity, and notifications of AIDS. RESULTS Comparing results from 1993-1995 with those for 1990-1992 shows a continuing increase in the incidence of Kaposis sarcoma with a doubling of the rates in both men and women. A dramatic increase in the incidence of squamous cell tumours of the conjunctiva was also observed, as well as a significant increase in the incidence of non-Hodgkins lymphoma in women. There was no apparent increase in risk for Hodgkins disease, myeloma, liver cancer, or cancer of the cervix. CONCLUSIONS The AIDS epidemic has had a dramatic effect on the profile of cancer. The changes in incidence involve several cancers previously linked to AIDS in North America and Europe.

The epidemiology of conjunctival squamous cell carcinoma in Uganda

As part of a larger investigation of cancer in Uganda, we conducted a case–control study of conjunctival squamous cell carcinoma in adults presenting at hospitals in Kampala. Participants were interviewed about social and lifestyle factors and had blood tested for antibodies to HIV, KSHV and HPV-16, -18 and -45. The odds of each factor among 60 people with conjunctival cancer was compared to that among 1214 controls with other cancer sites or types, using odds ratios, estimated with unconditional logistic regression. Conjunctival cancer was associated with HIV infection (OR 10.1, 95% confidence intervals [CI] 5.2–19.4; P<0.001), and was less common in those with a higher personal income (OR 0.4, 95% CI 0.3–1.2; P<0.001). The risk of conjunctival cancer increased with increasing time spent in cultivation and therefore in direct sunlight (χ2 trend=3.9, P=0.05), but decreased with decreasing age at leaving home (χ2 trend=3.9, P=0.05), perhaps reflecting less exposure to sunlight consequent to working in towns, although both results were of borderline statistical significance. To reduce confounding, sexual and reproductive variables were examined among HIV seropositive individuals only. Cases were more likely than controls to report that they had given or received gifts for sex (OR 3.5, 95% CI 1.2–10.4; P=0.03), but this may have been a chance finding as no other sexual or reproductive variable was associated with conjunctival cancer, including the number of self-reported lifetime sexual partners (P=0.4). The seroprevalence of antibodies against HPV-18 and -45 was too low to make reliable conclusions. The presence of anti-HPV-16 antibodies was not significantly associated with squamous cell carcinoma of the conjunctiva (OR 1.5, 95% CI 0.5–4.3; P=0.5) and nor were anti-KSHV antibodies (OR 0.9, 95% CI 0.4–2.1; P=0.8). The 10-fold increased risk of conjunctival cancer in HIV infected individuals is similar to results from other studies. The role of other oncogenic viral infections is unclear.