Research article
Is breast cancer prognosis inherited?
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* Corresponding author: Mikael Hartman mikael.hartman@ki.se
1 Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, P. O. Box 281, 171 77 Stockholm, Sweden
2 Stockholm Söder Hospital, Karolinska Institutet, Sjukhusbacken 10, 118 83 Stockholm, Sweden
3 Department of Epidemiology, Harvard University, 677 Huntington Avenue, Boston, 02115 MA, USA
Breast Cancer Research 2007, 9:R39 doi:10.1186/bcr1737
Published: 28 June 2007Abstract
Introduction
A genetic component is well established in the etiology of breast cancer. It is not well known, however, whether genetic traits also influence prognostic features of the malignant phenotype.
Methods
We carried out a population-based cohort study in Sweden based on the nationwide Multi-Generation Register. Among all women with breast cancer diagnosed from 1961 to 2001, 2,787 mother-daughter pairs and 831 sister pairs with breast cancer were identified; we achieved complete follow-up and classified 5-year breast cancer-specific prognosis among proband (mother or oldest sister) into tertiles as poor, intermediary, or good. We used Kaplan-Meier estimates of survival proportions and Cox models to calculate relative risks of dying from breast cancer within 5 years depending on the proband's outcome.
Results
The 5-year survival proportion among daughters whose mothers died within 5 years was 87% compared to 91% if the mother was alive (p = 0.03). Among sisters, the corresponding proportions were 70% and 88%, respectively (p = 0.001). After adjustment for potential confounders, daughters and sisters of a proband with poor prognosis had a 60% higher 5-year breast cancer mortality compared to those of a proband with good prognosis (hazard ratio [HR], 1.6; 95% confidence interval [CI], 1.2 to 2.2; p for trend 0.002). This association was slightly stronger among sisters (HR, 1.8; 95% CI, 1.0 to 3.4) than among daughters (HR, 1.6; 95% CI, 1.1 to 2.3).
Conclusion
Breast cancer prognosis of a woman predicts the survival in her first-degree relatives with breast cancer. Our novel findings suggest that breast cancer prognosis might be inherited.