NEW YORK (Reuters Health) - A woman's likelihood of surviving breast cancer is related to the survival rates among her first degree relatives with breast cancer, according to a new report.

"If the association turns out to be true ... it will open a new field for prognostication," Dr. Mikael Hartman from the Karolinska Institute, Stockholm, told Reuters Health.

Hartman and colleagues analyzed breast cancer prognosis among 2787 mother-daughter pairs and 831 sister pairs who had breast cancer diagnosed between 1961 and 2001.

The survival rate at 5 years for daughters whose mothers died within 5 years of diagnosis was 87 percent, compared with 91 percent for daughters whose mothers were alive 5 years after diagnosis, the team reports in the journal Breast Cancer Research.

The difference was greater for daughters whose mothers were younger than 70 years at diagnosis (83 percent versus 90 percent), the report indicates, and the difference for sisters was even more marked (70 percent versus 88 percent).

"So far, we can say ... that the simple question 'Did your mother die of breast cancer within 5 years?' can differentiate women into low and high risk groups," Hartman said.

"The difficult part is now to identify what is actually inherited," Hartman commented. It could be that women inherit some tumor characteristic or a particular aspect of the immune system. "It may simply turn out that some individuals are better or worse at fighting off tumors."

SOURCE: Breast Cancer Research, June 28, 2007.

REUTERS