Research published in the online journal Breast Cancer Research suggests that if a woman succumbs to breast cancer her daughters or sisters are over 60 percent more likely to die within five years if they develop the disease.

Mikael Hartman from the Karolinska Institute in Stockholm, Sweden led an international team, identifying 2,787 mother-daughter pairs and 831 sister pairs among women with breast cancer diagnosed between 1961 and 2001 from Sweden's national Multi-Generation Register.

They found that a woman's breast cancer prognosis predicts the survival of her first-degree relatives with breast cancer. Mothers surviving breast cancer after five years, had daughters with a 91 percent chance of surviving the disease. But only 87 percent of daughters whose mothers had died within five years survived. Being sister to a woman who had died of breast cancer within five years gave a 70 percent chance of survival from breast cancer, whereas chances improved to 88 percent if she had survived. Overall, a poor prognosis for a woman gave first-degree relatives a 60-80 percent higher chance of breast cancer mortality within the five-year timeframe.

Access to health care in Sweden is good irrespective of socio-economic status, so these factors are unlikely to have biased the findings. Women with a mother or sister who has had breast cancer are also likely to be more aware of the disease, making delays in seeking treatment unlikely. As well as genetics, other risk factors such as obesity and hormone replacement therapy probably play a role in the incidence and outcome of breast cancer. Dr Hartman says the findings are relevant to women with
newly diagnosed breast cancer, and to those treating them. The next step will be to understand what is inherited; tumor biology, response to therapy or vigilance of the immune system.