Smoking may increase the risk of dying early in pre-menopausal women with breast cancer, a research said.
"Overall, this work is monumental in advising patients about how smoking might affect breast cancer outcome," said co-author Yuko Minami from Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan.
This study included 848 patients admitted to a single hospital in Japan from 1997 to 2007. Active or passive smoking status was assessed using a self-administered questionnaire.
The patients were followed until December 31, 2010.
The researchers found that pre-menopausal women who smoked for more than 21.5 years had a 3.1-times higher risk of dying from any cause and a 3.4-times higher risk of dying from breast cancer.
These links were not apparent among post-menopausal women.
The increased risks seen in pre-menopausal women were especially relevant to women whose cancers expressed both the estrogen receptor and the progesterone receptor, the study said.
"Hopefully this paper will serve to reduce the number of breast cancer patients who continue to smoke," Minami said.
The results appeared in the journal Cancer Science.