Parental consanguinity and risk of breast cancer: a population-based case-control study.
BACKGROUND: An estimated 600 million people in the world have consanguineous parents. The effect of consanguinity on the risk of breast cancer is uncertain. The objective of this case-control study was to examine whether parental consanguinity and different levels of inbreeding affect the risk and pathology characteristics of breast cancer. MATERIAL/METHODS: Over a 36-month period, consecutive female breast cancer patients were recruited in the main cancer hospital in the United Arab Emirates. All were locally born Arabs with a tissue diagnosis of breast cancer. The controls were locally born Arabs without breast cancer matched to cases by sex, age, and residence. The coefficient of inbreeding (F) of both groups was determined from information they provided about their parents' kinship. RESULTS: The mean age of the 72 patients and 187 controls was 48.6 years (range: 25-86) and 48.5 years (range: 25-82), respectively (P = 0.46). Consanguinity rates of the patients and controls were 29.2% and 28.9% (P = 0.96) and the coefficients of inbreeding were 0.0117 and 0.0167 (P = 0.21), respectively. More closely inbred women (F > or = 0.0625) were less frequent among patients than controls, but the difference was not statistically significant (P = 0.12). The rates of pathological stage of disease, tumor histologies, and tumor grades were similar between more and less inbred patients. CONCLUSIONS: Parental consanguinity in Arabs, even when a marriage is between first cousins or double first cousins, was not associated with an altered risk of breast cancer.