Abstract
Breast cancer is the commonest site specific, malignancy affecting
women and the most common cause of cancer mortality in women
world wide. Our knowledge about breast cancer is evolving but it is
still limited with respect to its etiology and biology and with respect
to its features in individual countries and cultures.
The study was conducted to identify and determine the risk factors for breast
cancer in a Tertiary hospital in Nigeria. A retrospective case control study was
carried out in National Hospital Abuja. A total of 544samples were used in the
work comprising of 272 cases and 272 controls . The data was obtained directly
from patients case file. Information obtained were; Sex, Occupation, Weight,
Height, Parity, Age, Religion, Marital Status, Smoking, Family history of breast
cancer, Alcohol consumption, Menarche and Oral Contraceptive history. The data
was entered and analyzed using SPSS 15 version. The P value accepted as
significant was set at P < 0 .
1.0 INTRODUCTION
Breast Cancer constitutes a major public health issue globally with over 1 million
new cases diagnosed annually, resulting in over 400,000 annual deaths and about
4.4 million women living with the disease. It is the commonest site specific
malignancy affecting women and the most common cause of cancer mortality in
women worldwide.1,2
In Africa, Breast Cancer has overtaken cervical cancer as the commonest
malignancy affecting women and the incidence rates appear to be rising. 3,4
In
Nigeria for example, incidence rate has increased from 13.8–15.3 per 100,000 in
the 1980s, to 33.6 per 100,000 in 1992 and 116 per 100,000 in 2001.5
These
increases in incidence are due to changes in the demography, socio-economic
parameters, epidemiologic risk factors, better reporting and awareness of the
disease.
There is an international/geographical variation in the incidence of Breast Cancer.
Incidence rates are higher in the developed countries than in the developing
countries and Japan. Incidence rates are also higher in urban areas than in the
rural areas. While mortality rates are declining in the developed world (Americas,
Australia and Western Europe) as a result of early diagnosis, screening, and
improved cancer treatment programs, the converse is true in the developing world
as well as in eastern and central Europe 6,7
13
Breast cancer and its treatment constitute a great physical, psychosocial and
economic challenge in resource limited societies as found in Africa. The hallmark
of the disease in Africa are patients presenting at advanced stage, lack of adequate
mammography screening programs, preponderance of younger pre-menopausal
patients, and a high morbidity and mortality. 3,6
Pregnancy associated breast cancer is defined as breast cancer diagnosed during
pregnancy or lactation or one year post partum. Breast cancer and pregnancy can
be classified into three main situations; these are: breast cancer that is detected
during the evolution of pregnancy; breast cancer that is detected during lactation
or postpartum, and pregnancy in patients who have had a previous breast cancer.
Cancer complicates approximately 1 per 1000 pregnancies and accounts for onethird of maternal deaths during gestation. The prevalence of breast cancer during
pregnancy is increasing due to delayed onset of childbearing. Breast cancer is
diagnosed in approximately 1 in 3000 pregnancies. The incidence ranges from
0.76% to 3.8% of breast cancer cases. The median age of pregnant women
affected with breast cancer is 33 years. In a recent review in Nigeria, 12% of the
patients with Breast Cancer were pregnant or lactating and 74% were
premenopausal, making it the most frequently occurring malignancy during
pregnancy, along with cancer of the uterine cervix.5
14
1.2 INCIDENCE TRENDS WOMEN
1.2.1 Invasive breast cancer
Incidence rates of invasive female breast cancer for all races combined show three
distinct phases since 1975, when broad surveillance of cancer began:
Between 1975 and 1980, incidence was essentially constant;
Between 1980 and 1987, incidence increased by almost 4% per year;
Between 1987 and 2002, incidence rates increased by 0.3% per year.9
Much of the long-term underlying increase in incidence is attributed to changes in
reproductive patterns, such as delayed childbearing and having fewer children,
which are recognized risk factors for breast cancer. The rapid increase between
1980 and 1987 is due largely to greater use of mammographic screening and
increased early detection of breast cancers too small to be felt. Detecting these
tumors earlier has the effect of inflating the incidence rate because tumors are
being detected 1-3 years before they would have appeared if they continued to
grow until symptoms developed. During the introduction of mammography, from
1980 to 1987, incidence rates of smaller tumors (<2.0 cm) more than doubled,
while rates of larger tumors (3.0 cm or more ) decreased 27%.10 During this time,
the trend in diagnosis of smaller (<2.0 cm) tumors continued, increasing by 2.1%
per year from 1988 to 1999, and stabilized thereafter.11 A similar time trend was
seen with stage at diagnosis, with increases in the rates limited to cancers
diagnosed at a localized stage. The continued, though slight, increase in overall
15
breast cancer incidence since 1987 may reflect increase in the prevalencement
therapy (HRT).
1.2.2 Age
From 1980 to 1987, incidence rates of invasive breast cancer increased among
women aged 40-49 and 50 and older (3.5% and 4.2% per year, respectively).11
Since 1987, rates have continued to increase among women 50 and older, though
at a much slower rate. In contrast, the rates have slightly declined among women
aged 40-49. There has been relatively little change in the incidence rates of
invasive breast cancer in women younger than 40.
1.2.3 Race/ethnicity
During 1992-2002, overall incidence rates increased in Asian Americans/Pacific
Islanders (1.5% per year), decreased in American India/Alaska Natives (3.5% per
year), and did not change significantly among whites, African Americans, and
Hispanics/Latinas.11 This could be attributed to poor prognosis of aggressive
tumor common in African –American women8.
Incidence rates of breast cancer by tumor size differed between white and African
American women: African American women were less likely to be diagnosed
with smaller tumors (< 2.0 cm) and more likely to be diagnosed with larger
tumors (2.1-5.0 and > 5.0 cm) than white women.11
White women have a higher incidence of breast cancer than African American
women after age 35. In contrast, African American women have a slightly higher
16
incidence rate before age 35 and are more likely to die from breast cancer at every
age. Incidence and death rates from breast cancer are lower among women of
other racial and ethnic groups than among white and African women.
1.2.4 In situ breast cancer
Incidence rates of in situ breast cancer have increased rapidly since 198011 largely
because of increased diagnosis by mammography. Most of this increase
represents increased detection of ductal carcinoma in situ (DCIS), which from
1998 to 2002 accounted for about 85% of the in situ breast cancers diagnosed.
Incidence rates of DCIS increased more than sevenfold during 1980-2001.12 The
increase was observed in all age groups, although it was greatest in women aged
50 and older.11,12
Most cases of DCIS are detectable only through mammography, and the large
increases in DCIS incidence rates since 1982 are a direct result of
mammography’s ability to detect cancers that cannot be felt. Although increase in
both invasive breast caner and DCIS incidence rates have slowed since the mid1980s,13the temporal increase in DCIS since 1982 is larger than the increase in
invasive breast cancer.
Lobular carcinoma in-situ (LCIS) is less common than DCIS, accounting for
approximately 12% of female in situ breast cancers diagnosed from 1998 to
2002.11 Similar to DCIS, the overall incidence rate of LCIS has increased more
rapidly than the incidence of invasive breast cancer.11 This increase has been
limited to women older than 40 and largely to postmenopausal women.,12.14
17
1.3 Mortality trends –women
The death rate from breast cancer in women has decreased since 1990:
Between 1975 and 1990, the death rate for all races combined increased by
0.4%annually;
Between 1990 and 2002, the rate decrease by 2.3% annually.15
The percentage of decline was larger among younger age groups. From 1990 to
2002, death rates decreased by 3.3% per year among women younger than 50, and
by 2.0% per year among women 50 and older.15 The decline in breast cancer
mortality since 1990 has been attributed to both improvements in breast cancer
treatment and to early detection.16,17
African American women and women of other racial and ethnic groups, however,
have benefited less than white women from these advances. From 1990 to 2002,
female breast cancer death rates declined by 2.4% per year in whites, 1.8% in
Hispanics/Latinas, 1.0% in African Americans and Asian Americans/Pacific
Islanders, and did not decline in American Indian/Alaska Natives.18 A striking
divergence in long-term mortality trends is seen between African American and
white females. The disparity in breast cancer death rates between African
American and white women appeared in the early 1980s; by 2002, death rates
were 37% higher in African Americans than in white women.15
1.4 Incidence and mortality trends –men
18
Although breast cancer in men is a rare disease, accounting for less than 1% of
breast cancer case in the US, between 1975 and 2002, the incidence rate among
males increased 1.1% annually. 11 The reasons for the increase are unknown and
are not attributable to increased detection. Similar to female breast cancer, the
incidence of male breast cancer increases with age.19 Men however are more
likely than women to be diagnosed with advanced disease and thus have poorer
survival.19 Death rates from male breast cancer have remained essentially constant
since 1975. 15
Male breast cancer is an uncommon disease although the incidence has increased
over the past 25 years. Less than 1% of all breast cancer patients are male. Rates
of male breast cancer vary widely between countries: in Uganda and Zambia the
annual incidence rates are 5% and 15%, respectively of all breast cancer cases.
These relatively high rates have been attributed to endemic infectious diseases
causing liver damage, leading to hyperestrogenism. By contrast, the annual
incidence of male breast cancer in Japan is less than five per million, in parallel
with the lower than average incidence of female breast cancer in that country.
Jewish men are the only racial group with a higher than average incidence
(2•3/100 000 per year), irrespective of living in Israel or the USA.
Risk factors for Breast Cancer include; Genetic (BRCA2, Klinefelter’s
syndrome), Lifestyle (Obesity, Alcohol, Estrogen intake) , Work (High ambient
temperature, Exhaust emissions) and Disease (Testicular damage, Liver damage,
Radiotherapy to chest. The predominant histological type of disease is invasive
ductal, which forms more than 90% of all male breast tumors.29
19
1.5 PROBLEM STATEMENT
Breast cancer unlike cervical cancer has no precise etiological agent. It therefore
constitutes a major public health issue globally. Our knowledge about breast
cancer is evolving, but it is still limited with respect to its etiology and biology
and with respect to its features in individual countries and cultures.
All efforts are geared towards early diagnosis, prompt and standardized treatment
to reduce the disease burden of advanced disease in African women, majority who
are worse hit in the most productive part of their life time20. Therefore there is the
need to elicit possible risk factors for breast cancer in Nigeria.
1.6 JUSTIFICATION FOR THE STUDY
The breast is very important in the life of a woman. It is the essential part of the
body which nourishes a new born. It is one of the part of the body which attracts
the opposite sex amongst adults. In Africa, a woman without breast is regarded as
incomplete.
Breast cancer starts with some of the cells in the breast growing abnormally and
in most cases, it isn’t clear what causes normal breast cells to become
cancerous.60 Doctors know that only 5-10% breast cancers are inherited yet
genetic mutations related to breast cancer aren’t inherited.
20
The study was designed to identify, determine as well as establish risk factors that
predispose one to breast cancer in Nigeria. Results obtained will contribute to
public health consciousness to risk factors for breast cancer in Nigeria
1.7 OBJECTIVES
General Objective:
To identify the major risk factors for Breast cancer in Nigeria
Specific Objectives:
1. To identify the risk factors for breast cancer
2. To determine the association of risk factors contributing to Breast cancer.
3. To establish major risk factors contributing to Breast Cancer in
Nigeria