Despite a number of major breakthroughs in the field of genetics and cancer research, breast cancer still remains a killer disease. While lifestyle and environment can significantly contribute to the development of breast cancer, heredity does play an important role. And so far as hereditary breast cancer is concerned, mainly two genes account for the development of the disease. Genetic risk factors for breast cancer are closely associated with two genes: BRCA1, which stands for BReast CAncer gene one, and BRCA2, or BReast CAncer gene two.
Let's explain how BRCA gene 1and 2 contribute to the genetic risk for breast cancer.
In their normal state, BRCA1 and 2 perform an important task- they keep the growth of breast cells at a normal level. In this way they also prevent the growth of cancer cells. Sometimes BRCA genes 1 and 2 have abnormalities or mutations. People are either born with abnormal BRCA gene 1 and 2 or they acquire abnormalities during lifetime. In any case, mutated BRCA1 and BRCA2 genes enhance the genetic risk for breast cancer. In fact BRCA1 and BRCA2 mutations are the cause for some 10% of all breast cancer cases.
breast cancer hereditary
Breast cancer is the most common cancer and the second leading cause of cancer deaths in women in the United States. In 2008, approximately 184,450 patients were estimated to be diagnosed with invasive cancer, and an estimated 40,930 were estimated to die of this disease. Furthermore, over 50,000 female carcinoma in situ breast cases would have been diagnosed. The etiology of breast cancer is poorly understood with multiple genetic and environmental factors involved in the initiation and progression of cancer.
Scandinavian Twin Study: For years, there has been a hot debate as to whether the cause of breast cancer is genetic or environmental. Then in 2000, Lichtenstein and his colleagues at the Karolinska Institute in Sweden published their study of 44,788 pairs of twins from the Swedish, Danish, and Finnish twin registries. In this study, they looked at cancer risk with 28 different types of cancers and did statistical modeling of genetic and hereditary contributions in eleven different cancer types. For breast cancer, they clearly showed that only 27% of cancer cases were due to genetic factors. This was an even lower hereditary component than other common cancers such as prostate and colorectal. This study and others have confirmed the fact that over 70% of breast malignanciess are influenced by environmental factors.
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Mike Jsimon, M.D.
University of Maryland
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