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Keywords:

  • breast cancer;
  • ethnicity;
  • age

Abstract

  1. Top of page
  2. Abstract
  3. Material and Methods
  4. Results
  5. Discussion
  6. References

Black women have lower age-standardized breast cancer incidence rates than White women in the United Kingdom. However, little is known about such differences in risk in separate age groups. Records on female residents of South East England diagnosed with breast cancer between 1998 and 2003 were extracted from the Thames Cancer Registry database. Age-specific incidence rates were calculated for each 5-year age group using 2001 Census population data for White, Black Caribbean and Black African women. Black Caribbean and Black African breast cancer patients were younger than both the White patients and those with no ethnicity recorded. Black Caribbean and Black African women in the population also had a younger age profile than White women. The computed age-specific incidence rates in women aged under 50 were similar in the different ethnic groups, whereas in women aged 50 and over White women had higher rates. The younger age of Black Caribbean and Black African breast cancer patients in South East England reflects the younger age of these populations, rather than an increased risk of disease at younger ages.

Age-adjusted breast cancer incidence rates are lower in Black women than White women in the United States1, 2 and the United Kingdom.3, 4 A higher age-specific incidence rate in Black women aged under 40 has been reported in the United States.5–8

A hospital study in North East London reported that Black women with breast cancer were younger than White breast cancer patients.9 However, the local population data were only available for broad age groups.10 A large population-based study has not yet investigated the risk of breast cancer in different age groups in the United Kingdom. This study therefore aimed to examine whether there is a difference in the age at which Black Caribbean, Black African and White women are diagnosed with breast cancer that is unrelated to differences in the population age structures.

Material and Methods

  1. Top of page
  2. Abstract
  3. Material and Methods
  4. Results
  5. Discussion
  6. References

In the United Kingdom, cancer registries record the occurrence of cancer in their resident populations. In the area covered by the Thames Cancer Registry, registration is initiated by clinical and pathological information received from hospitals and by information about deaths provided by the National Health Service (NHS) Central Register through the Office for National Statistics. Trained cancer registration officers then extract further information on demographic details, disease stage and treatment from the medical records. Data are quality assured as they are added to the central database. Hospital Episode Statistics (HES) data come from hospital Patient Administration Systems and include patient, clinical, administrative and geographical details. Self-assigned ethnicity was introduced to the HES data in April 1995 using the codes from the England and Wales Census.

Records on female breast cancer cases resident in South East England who were diagnosed between 1998 and 2003 were extracted from the Thames Cancer Registry database. Ethnicity information from inpatient HES records was linked to the registry records using NHS number (a unique person identifier), or sex, date of birth and postcode of residence. If there was no link, ethnicity information routinely recorded by the Thames Cancer Registry was used, if available. Population data on female residents of the same area of South East England were obtained from the 2001 Census (the most recent England and Wales census) by age and ethnic group. Age-specific rates were calculated for each 5-year age group, and age-standardized incidence rate ratios (ASRRs) were calculated for Black Caribbean and Black African women compared with the baseline of White women in 10-year age groups. The ASRRs are therefore the ratio of breast cancer incidence in Black Caribbean or Black African women compared with White women of the same age.

Results

  1. Top of page
  2. Abstract
  3. Material and Methods
  4. Results
  5. Discussion
  6. References

There were 31,698 White, 659 Black Caribbean and 345 Black African women diagnosed with breast cancer between 1998 and 2003. During this period there were also 20,079 female South East England residents diagnosed with breast cancer who had no ethnicity recorded. The proportion of women without ethnicity information varied by age: 31% of those aged under 50 did not have an ethnic code recorded, compared with 37% of those aged 50 and over.

Figure 1a shows the age distribution of the breast cancer patients in White, Black Caribbean and Black African ethnic groups, along with those patients who had missing ethnicity information. The Black Caribbean and Black African patients were younger than both the White patients and those with no ethnicity recorded.

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Figure 1. Age distribution of (a) female breast cancer cases, diagnosed 1998–2003, (b) female population from 2001 Census, South East England by ethnic group. (c) Age-specific incidence rate per 100,000 of female breast cancer.

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The population age distribution (Fig. 1b) shows that in South East England Black Caribbean and Black African women have younger age profiles than White women. Table 1 compares the mean and median ages of women in different ethnic groups with breast cancer and in the population. Black Caribbean women were diagnosed with breast cancer on average 7 years younger than White women, while Black African women were on average 15–16 years younger. These differences are similar to those between the population groups: the Black Caribbean population were around 4–6 years younger, and the Black African population were 11–14 years younger than the White population.

Table 1. Mean and median age (years) of female breast cancer cases diagnosed 1998–2003, and female population from 2001 Census, South East England, by ethnic group
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The computed age-specific rates shown in Figure 1c are too low, because cases with missing ethnicity information did not have a corresponding population denominator. However, the computed rates in women aged under 50 were similar in the different ethnic groups. Because of the age distribution of the patients with no ethnicity information, the age-specific rates for the older groups are more likely to be underestimated than the younger ages. The ASRRs (Fig. 2) show a very strong age effect in Black African women, with younger women having incidence rates more similar to White women of the same age. This was also seen in Black Caribbean women, although women aged 80 years and over had rates similar to White women.

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Figure 2. Age-standardized rate ratios (ASRR) and 95% confidence intervals for female breast cancer diagnosed 1998–2003, South East England, by age and ethnic group. White women as baseline.

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Discussion

  1. Top of page
  2. Abstract
  3. Material and Methods
  4. Results
  5. Discussion
  6. References

Black Caribbean and Black African women are diagnosed with breast cancer at a younger average age than White women, or those without ethnicity information recorded in South East England. However, breast cancer incidence rates are similar in Black Caribbean, Black African and White women aged under 50 years. The difference in average age is due to the differences in the population age structures. The younger average age of Black Caribbean and Black African women in the population is due to their recent history of migration to the United Kingdom, with large numbers of working age adults arriving in the 1950s and 1960s.11

This study used data from a large, ethically diverse population, and was able to adjust for the age structure of the population. A limitation of the study was that ethnicity information was not recorded for a large number of breast cancer patients. These patients were on average slightly older than the White patients, and were therefore unlikely to affect the analyses on the younger patients.

The younger age of Black Caribbean and Black African breast cancer patients in South East England reflects the younger age of these populations rather than increased risk of disease at younger ages. However, women from all ethnic groups need to be aware of the signs and symptoms of breast cancer, and health practitioners should recognize the comparable risk of breast cancer in younger Black and White women. This information will also be useful for breast cancer awareness and community groups.

References

  1. Top of page
  2. Abstract
  3. Material and Methods
  4. Results
  5. Discussion
  6. References