From The Editors  What's New At MEDICC  Spotlight On...  MR Interviews…  Health News from Cuba  Cuban Medical Research

CUBAN MEDICAL RESEARCH

Breast Cancer Risk in Cuba
Yaima Galan Alvarez, MPH 1
Leticia Fernández Garrote, MD, PhD 2
Priscila Torres Babié, MD 3
Marta Guerra Yí, BS 4
Mariela García Jordán, MD, MPH 5

ABSTRACT: Breast Cancer is a health problem in Cuba because of high incidence and mortality rates. The National Cancer Registry (NCR), created in Cuba in 1964, is the ideal tool for assessing the magnitude of the problem and for helping to make decisions for early diagnosis. Method: Based on the data provided by the NCR, calculations were made of specific rates by age groups (under 35, 35-49, 50 and older). Crude and adjusted rates were calculated by the direct method, as well as truncated rates for the 35-64 age groups. Rates are expressed in terms of the number of cases per 100 000 women per year, and are compared by provinces. A trend analysis of incidence in the period 1977-2000 was performed using a Poisson regression model. Results: An annual average of 2 220 new cases were diagnosed, with a rate of 40.02 cases per 100 000 inhabitants. The highest risk group was that of 65 years or older, which represents 36% of all the diagnosed cases, with an average of 801 cases and a rate of 151.5 for every 100 000 women. There is an increasing trend ( p < 0.05) with a 2% annual average change (95% Confidence Interval, 1.5-2.7). The truncated rate between 35 and 64 years of age was 71.6 per 100 000 women in the 1998-2000 period. The analysis of these results assists specialists and health decision makers to prioritize actions in the cancer control program.

Introduction

Today, breast cancer is the world’s second most frequent cause of cancer and the first cause among women. Approximately 1.05 million new cases are diagnosed every year (22% of the total cancers in women), while 375 000 women die as a result of this disease every year. There are geographical differences, with the highest rates in North America, Northern Europe and Oceania, intermediate rates in Central and South America, and South and Eastern Europe, while the lowest rates are found in Africa and Asia , . Increased incidence is apparent in many countries, with the greatest changes generally appearing in countries with lower rates. The majority of reports in current literature argue that hereditary factors are associated with less than 5% of the cases, while other authors speak of a 10% association. Most risk factors mentioned for breast cancer are related to women’s reproductive activity: early menarche, nulliparity or first childbirth at a late age, late menopause, and others such as diet, physical exercise, and hormonal or exogenous factors 4.

The worldwide mortality incidence ratio is about 36% 1 . Due to this relatively good prognosis, breast cancer is the most prevalent cancer localization in the world. Parkin 1 estimates that there are 3.7 million women alive in the world who have been diagnosed with this type of cancer in the last five years.

The socio-economic development of Latin American and Caribbean countries, as well as the results of the changes in women’s reproductive life in the last 50 years, have turned breast cancer into a growing health problem in this region 4 . Cuba shows high incidence and mortality rates in breast cancer 5 , and these indicators allow us to measure the risk of developing this condition and the related risk of death from it. Being able to estimate the risk of breast cancer in Cuban women and its behavior over time will contribute to quantify this health problem, to define priorities for preventive actions, and to assess the results of the breast cancer control program.

Materials and method

The data recorded by the Cuban National Cancer Registry (NCR) for 1998-2000 were used to estimate the incidence of breast cancer in Cuba. Age-specific rates were calculated for four age groups: under 30, 30-49, 50-64, 65 and older. Incidence rates were computed by direct method of adjusting both to the 1981 Cuban population and to the world standard population. The truncated rate in age groups between 35 and 64 was also calculated. Rates were expressed in number of cases per 100 000 women per year, and were compared by provinces. A trend analysis between 1977 and 2000 was made through the adjustment of the Poisson regression model.

Results

An average of 2 222 new cases were diagnosed every year in the 1998-2000 period, for an annual average rate of 40.0 cases per 100 000 inhabitants. Table 1 shows the distribution of breast cancer cases diagnosed in this period according to age groups, and indicates that the risk of this disease is very low in women under age 30, and increases from this age forward. The highest risk group is for women over 65, with an average of 801 cases in the 1998-2000 three-year period, and an average annual rate of 151.5 per 100 000 women. This group represents 36% of the cases diagnosed.

Table 1Incidence of breast cancer in Cuba by age groups 1998-2000

1 to the world population

Figure 1 shows the distribution of crude and adjusted incidence rates of breast cancer over time, as well as adjusted mortality rates. There is an increasing trend in incidence for both rates (p <0.05), with a 2% (95% RI, 1.5-2.7) annual average change for crude rates, and 0.9% (95% RI, 0.4-1.4) for adjusted rates. A decline in rates was observed between 1993 and 1995. Mortality has remained stable, with a 0.06 tendency (95% RI, -0.01; 1.37), with a minimum value of 13.6 and a maximum of 18.0 for 1977-2000.

Figure 1: Crude and adjusted incidence rates of breast cancer in Cuba (1977-2000)

The largest risk of developing breast cancer in Cuba in the 1998-2000 period was observed in Havana City, followed by Villa Clara and Matanzas Provinces, where 30% of cases were diagnosed. The risk is less than 20 per100 000 women in the provinces of Las Tunas and Guantanamo, but the mortality incidence ratio is higher than 70%. The truncated rate between 35 and 64 years of age was 71.6 per 100 000 women in the 1998-2000 period.

The risk of death is higher for Havana City and the eastern provinces.

Figure 3:Geographical distribution of Breast Cancer Incidence, Cuba (1998-2000)

Discussion

The existence of a National Cancer Registry in Cuba, created in 1964, has made it possible to estimate breast cancer risk for Cuban women by age and geographical region, and to follow the behavior of the condition over time. Risk increases with time, mainly attributable to the 60-or-older group. This pattern is repeated worldwide, where about 75% of breast cancer cases are diagnosed in women over 50 4 . A slight stability can be found in breast cancer incidence in women around 50, which can be associated with the appearance of menopause.

The fact that a large number of Cuban women either work or study, and have become active in society over the last 40 years, results in a change towards more Westernized life styles. Urbanization increased in Cuba from 73.9% in 1990 to 75.2% in 2000 4, and though the relationship between health and urbanization is complex, it is undeniable that these elements are closely connected. Health improvement brought about by such beneficial effects of urbanization as sanitation, electrification and a greater availability and accessibility of health services, is associated, as a rule, with lifestyle modifications which are determinants of cancer risk. Epidemiological research reveals a positive relationship between breast cancer and socioeconomic factors 4. Such reproductive factors as nulliparity, small number of children, late childbirth, late menopause, and to a lesser degree, diet 5,6, can be held partially responsible for this positive association, since these characteristics are more commonly found in women with a higher socioeconomic status. All these factors partly account for the breast cancer increase found in Cuba.

It is clear that increases in rates of the disease parallel increases in industrialization, mainly in those areas where rates were low. The annual increase worldwide is estimated to average 0.5%, which means that there will be 1.25 million new cases in 2010 1. The percentage of increase is higher in Cuba (0.9%), which means 2 378 new cases should appear 2010. Breast cancer risk increased for Cuban woman, from 24.4 new cases per 100 000 in 1977, to 31.4 in 2000. This increase is similar in other developing countries where tendency studies have been carried out 4. A 1% annual increase is reported in Bombay between 1964 and 1985, a 2.7% increase in Shanghai 5 between 1972-1974 and 1992-1993, while a 3.6% increase is reported in Singapore between 1968 and 1992.

One reason for the incidence variation among provinces could be factors related to different environmental exposures and life styles. Breast cancer risk is associated with a high socio-economic level 4. In the United States, for instance, risk variation related to educational level or annual income can be almost completely explained by the different distribution of such factors as parity, menstruation and menopause age, obesity and alcohol consumption 4. Previous research 5 on the prevalence of risk factors in Cuba showed that over 50% of the population had a mid-level socio-economic status. The eastern provinces showed the largest proportion of people with a low socio-economic status, while Havana City had the most with a higher status. Significant differences were found among women, in terms of number of children, age at birth of the first child, proportion of women with no children, early or late menarche and menopause, number of abortions, and history of g ynecological pathologies. These differences are associated with the fact that the western and central provinces show a higher socioeconomic level, are predominantly white (a historical factor related to socio-economic status), women have their first child after 20, and they have no more than three children. Behavior of women in the eastern provinces is the opposite.

In addition, the mortality-incidence ratio is higher in the eastern provinces, except for Santiago de Cuba. This could be a factor to consider in assessing the results of the breast cancer control program in those provinces. The truncated rate for the 35-64 age groups is double that of the incidence rate, reflecting the high risk for breast cancer in these age groups.

The analysis of these results should guide specialists and decision-makers as they prioritize the cancer control program’s actions and resources for higher risk geographical regions and age groups.

References

1 Parkin DM, Bray FI, Devesa SS. Cancer burden in the year 2000. The global picture. European Journal of Cancer 2001; 37:4-66.

2 J.Ferlay, F. Bray, P. Pisani and D.M. Parkin. GLOBOCAN 2000: Cancer Incidence, Mortality and Prevalence Worldwide, Version 1.0. IARC CancerBase No. 5. Lyon, IARCPress, 2001.

3 Parkin DM. Global cancer statistics in the year 2000. Lancet Oncol 2001; 2:533-46.

4 Key TJ, Verkasalo PK, Banks E. Epidemiology of breast cancer. Lancet Oncol 2001 Mar;2(3):133-40

5 Robles SC, Galaris E. Breast cancer in Latin America and the Caribbean. Rev Panam Salud Publica 2002 Mar;11(3):178-85.

6 Cáncer en Cuba. 1997-1998. Registro Nacional de Cáncer. Instituto Nacional de Oncología y Radiobiología, la Habana 2001, ISBN 959-7132-70-2

7 Smith B. The Breast. Curr Probl Obstet Gynecol Fertil 1996; 9(1):7-9.

8 Cuba. Estadísticas seleccionadas 2000 . Oficina Nacional de estadísticas. Marzo 2001. ISBN 959-7119-16-1

9 Van Loon J, Goldbohm A, Van Den Brandt P. Socioeconomic status and breast cancer incidence: A prospective cohort study. Int J Epidemiol 1994;23(5):899-905.

10 Kelsey JL, Gammon MD. Epidemiology of breast cancer. Epidemiol Rev 1990; 12:28-240.

11 American Institute for Cancer Research (eds). Patterns of Cancer. In: Food, Nutrition and the Prevention of Cancer: A global perspective. 1997: 35-52.

12 Parkin DM. Cancer in developing countries. Cancer Surv 1994, 19/20, 519-561.

13 Jin F, Devessa SS, Chow W, et.al. Cancer Incidence trends in urban Shanghai, 1972-1994: an update. Int J Cancer 1999, 83;435-40.

14 Karjalinen S, Pukkla E. Social class as a prognostic factor in breast cancer survival. Cancer 1990, 66;819-826

15 Heck KE, Pamuk Er. Explaining the relation between education and postmenopausal breast cancer. Am J Epidemiol 1997, 145:366-372

16 Lorenzo-Luaces P, Galán Y, Abascal ME. Técnicas estadísticas multivariadas en la investigación epidemiológica. Ejemplo en la prevalencia de factores de riesgo de cáncer en Cuba. Rev Cubana Oncol 1995, 11(1);55-60

1. BS in Mathematics. Head of the National Office, National Cancer Registry in Cuba.

2 . Second degree specialist in Biostatistics. Vice Director for Research. National Institute of Oncology and Radiology, Havana.

3 . First degree specialist in Oncology. National Office, National Cancer Registry.

4 . BS in Mathematics. National Office, National Cancer Registry.

5 . National Office, National Cancer Registry.