Background: Black South African women are known to have a high usage rate of
injectable contraceptives. Breast cancer is the second leading cancer after malignant
cervical neoplasms in black South African women. There is evidence that sex
hormones are associated with an increased risk of developing breast cancer. In the
Western Cape, investigators suggested that injectable contraceptives, more
specifically DMPA, may increase breast cancer risk. In another study conducted in the
same province, a weak association between breast cancer and women taking
combined oestrogen/progesterone oral contraceptives was found, though no risk
associated with injectable progestogen contraceptives (DMPA) was confirmed.
Study Objective: This study aimed to determine whether there is an association
between hormonal contraceptive use and an increased risk of cancer of the breast.
Methods: Data was obtained from an ongoing case control study set up by
MRC/Wits/NHLS Cancer Epidemiology Research Group (CERG) in 1995 to
investigate risk factors associated with cancer among the black population in
Johannesburg. Data was processed using STATA, version8 and analysed using
univariate, bivariate and multivariate unmatched logistic regression models.
Results: There was evidence that an overall use of oral contraceptives increases the
risk of breast cancer; cases (n= 221), controls :( n= 153), OR=2.01 (95% CI:1.45,
2.80), p<0.0001.
There was evidence of an association between use of injectable contraception and the
risk of breast cancer; cases (n=244), controls (n=202), OR=1.51(CI: 1.14, 2.01),p=0.004 Surprisingly, no other use characteristic of either hormonal contraceptive method was
statistically significantly associated with the risk of breast cancer in our dataset.
The combined use of both oral and injectable contraception was associated with an
increased risk of breast cancer, OR=1.68(1.21, 2.33), p =0.002. There was a strong
effect modification (interaction) between oral contraceptive use and injectable
progesterone associated with the risk of breast cancer, (p=0.008).
Conclusion: After adjusting for all potential risk and confounding factors, as
collected in the dataset, there was evidence of an association between combined oral
contraceptive use and breast cancer. An association between cancer of the breast and
overall use of injectable progesterone use was also established. There was evidence of
association between the use of both hormonal contraceptive methods and an increased
risk of breast cancer. However, whether these findings reflect the reality in terms of
causal relationship or are the result of bias must be ascertained.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/5740 |
| Date | 10 October 2008 |
| Creators | Rubanzana, Wilson |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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