BRCA1 and BRCA2 Mutations Are Relatively Frequent in Nigerian Breast Cancer Patients
In situations where genetic medicine has the potential to provide health benefits, they’ve largely been confined to the developed world. Hereditary Breast and Ovarian Cancer syndrome is an excellent example. Women with a strong personal and/or family history of breast and ovarian cancer have access to technology – genetic testing for mutations in the BRCA1 and BRCA2 genes – that can yield information allowing the targeting of preventative and intensive screening efforts to a subset of women at highest risk.
Although the technology and expertise to give hope to women at particularly high risk is beginning to mature in the U.S. and other developed nations, that is not the case in the developing world. Nevertheless, efforts from a few physicians and researchers aspire to begin to make a dent in this problem.
The case of Nigeria may turn out to be very important. There is a modest amount of published research related to the impact of BRCA1 and BRCA2 gene mutations on breast and ovarian cancer risk in Nigeria. Virtually all of it has come from the efforts of Dr. Funmi Olopade of the University of Chicago and her colleagues and collaborators both there and in Nigeria.
Women of African ancestry who develop breast cancer do so typically at a younger age than other groups and have higher mortality rates from the disease. Although early onset (i.e., before menopause) breast cancer can be suggestive of Hereditary Breast and Ovarian Cancer syndrome caused by a BRCA1 or BRCA2 mutation, previous studies looking for BRCA1/2 mutations in women of African descent with breast cancer have suggested very low mutation rates (when women entering the studies were not selected for extremely early onset cancer).
However, a new study from Dr. Olopade’s group has revealed evidence that BRCA1/2 mutations are more common than was generally previously thought in women with breast cancer in Nigeria.
They studied 434 breast cancer cases from University College Hospital in Nigeria. All consecutive female breast cancer cases during an 8 year period were offered entrance to the study. Also, eight men with breast cancer were enrolled in the study. The average age of breast cancer diagnosis was approximately 46 years old and about one in ten patients reported a breast cancer family history. The researchers looked for mutations and larger deletions and duplications in the BRCA1 and BRCA2 genes in a comprehensive manner and were pretty conservative in what they called a “deleterious” or real mutation.
Surprisingly, in this group of “all comers” – i.e., consecutive breast cancer patients unselected for family history or other characteristics – about 11 percent had a deleterious BRCA1 or BRCA2 mutation (~7 percent in BRCA1 and ~4 percent in BRCA2).
A rate of 11 percent is higher than expected in this group of patients and probably underestimates the true rate given that a number of the other patients had variants of uncertain significance in one of the genes.
There is much work to be done – both in assessing the impact of BRCA1 and BRCA2 in other populations of African descent and also in putting this information to work to improve health in places that, unfortunately, are all-too-often extremely resource poor.
How We Know This:
Fackenthal JD, Zhang J, Zhang B, et al. High prevalence of BRCA1 and BRCA2 mutations in unselected Nigerian breast cancer patients. International Journal of Cancer 2011 (Published online ahead of print Oct 27 2011)
