Background: The aim of the present study was to define the proportion of different levels of family history in a cohort of consecutive breast cancer patients from the Stockholm region, and to assess whether familial breast cancer has phenotypic traits different from those of sporadic patients.
Methods: All incident breast cancer patients in a 19-month period were eligible for the study and 70% (489/696) participated. The family history and clinical parameters were obtained from questionnaires and medical records.
Results: In total 35% had a family history. Age at onset was 58.9 years in the familial group vs. 60.7 years in the sporadic patients (P = 0.14) and 8% of the familial patients had bilateral breast cancer compared to 4% in the sporadic group (P = 0.08). There were 31% node positive tumors in the sporadic group vs. 22% in the cases with family history (P = 0.04). Hormonal background, treatment and prognosis (median follow-up 4.7 years) were not related to family history.
Conclusion: In addition to high-risk familial breast and breast-ovarian cancer, constituting about 10% of all breast cancer cases, another 25% of the breast cancer cases have a family history, a group hypothetically valuable for association studies on low-risk genes. In contrast to previous reports, we did not observe a relationship between family history and phenotypic traits. A possible explanation for this can be different study design. The considerable heterogeneity in familial breast cancer means that different criteria for familiality can influence the result. Furthermore, our study was prospective and population based and included paternal inheritance.