Abstract
BackgroundApproximately 30 % of all breast cancer is at least partly attributed to hereditary factors. Familial breast cancer is often inherited in the context of cancer syndromes. The most commonly mutated genes are BRCA1 and BRCA2 in hereditary breast and ovarian cancer syndrome. The genetic background in families with hereditary breast cancer without predisposing germ line mutations in BRCA1 and BRCA2 (non-BRCA families) is still to a large extent unclear even though progress has been made. The aim of this study was to compare cancer proportions in familial non-BRCA hereditary breast cancer compared to the general population in search of putative new breast cancer syndromes.MethodsPedigrees from 334 non-BRCA hereditary breast cancer families in the county of Stockholm, Sweden, were investigated and the distribution of cancer diagnoses other than breast cancer was compared with the distribution of cancer diagnoses in the general Swedish population in two reference years, 1970 and 2010. A cancer diagnosis was regarded as overrepresented in the non-BRCA families if the confidence interval was above both population reference values.ResultsWe found that endometrial cancer was overrepresented in the non-BRCA families with a 6.36 % proportion (CI 4.67–8.2) compared to the proportion in the general population in the reference years 1970 (3.07 %) and 2010 (2.64 %). Moreover tumours of the ovary, liver, pancreas and prostate were overrepresented.ConclusionIn conclusion, we found an overrepresentation of endometrial cancer in our cohort of hereditary non-BRCA families. Our result supports previous inconsistent reports of a putative breast and endometrial cancer syndrome. An association has been suggested in studies of families with several cases of breast cancer in close relatives or bilateral breast cancer. To clarify this issue we suggest further studies on a breast and endometrial cancer syndrome in cohorts with a strong pattern of hereditary breast cancer. Identifying new breast cancer syndromes is of importance to improve genetic counselling for women at risk and a first step towards detection of new susceptibility genes.
Highlights
Breast cancer is the most common form of cancer in women, the incidence varies greatly, being highest in developed countries, and increasing in developing nations
We found an increased incidence of endometrial cancer representing a proportion of 6.36 % (CI 4.67–8.2) in the study families compared to the incidence in the general population in the reference years 1970 and 2010 (3.07 % in 1970, 2.64 % in 2010)
The main finding of the present study is that endometrial cancer was overrepresented in the study population of families with hereditary non-BRCA breast cancer compared to the reference population, supporting the earlier findings of a putative breast cancer and endometrial cancer syndrome [31]
Summary
Breast cancer is the most common form of cancer in women, the incidence varies greatly, being highest in developed countries, and increasing in developing nations. The age of onset in these families is lower than in the case of sporadic breast cancer [3, 4]. Depending on the number of affected relatives and the age at onset, the conferred risk ranges from almost doubled to fivefold compared to the 10 % population risk [3]. The most commonly mutated genes are BRCA1 and BRCA2 in hereditary breast and ovarian cancer syndrome. The genetic background in families with hereditary breast cancer without predisposing germ line mutations in BRCA1 and BRCA2 (non-BRCA families) is still to a large extent unclear even though progress has been made. The aim of this study was to compare cancer proportions in familial non-BRCA hereditary breast cancer compared to the general population in search of putative new breast cancer syndromes
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