New research suggests that young women who smoke and who have smoked one pack of cigarettes a day for 10 years or more have a much higher risk for estrogen receptor-positive breast cancer - the most common form of the disease - compared with women who have smoked for a shorter period.
Women who had ever smoked (more than 100 cigarettes in their lifetime) had a 30% increased risk of breast cancer overall, compared with never smokers (fewer than 100 cigarettes in their lifetime).
However, the researchers found that young women who were current or recent smokers, and who had been smoking one pack of cigarettes a day for at least a decade, were 60% more likely to develop estrogen receptor-positive breast cancer, compared with women who had smoked for fewer years and those who had a history of fewer pack-years.
The researchers found no link between smoking in young women and the risk of triple-negative breast cancer.
The research team, led by Dr. Christopher Li of the Fred Hutchinson Cancer Research Center in Seattle, WA, said quite a bit of research has associated smoking among young women with an increased risk of breast cancer. But they say few studies have assessed the link between smoking and subtypes of breast cancer.
For their study, published in the journal Cancer, the investigators analyzed 778 women who had estrogen receptor-positive breast cancer, 182 women with triple-negative breast cancer, and 938 women who were cancer-free.
When the breast cancer cells have a significant number of receptors for estrogen, this is classed as estrogen receptor-positive breast cancer. This type of cancer is more likely to respond to hormonal therapies.
Triple-negative breast cancer means the breast cancer cells are not positive to receptors for estrogen, progesterone or HER2. This form of breast cancer is usually more aggressive.
All patients were aged between 20 and 44 years, and those with breast cancer were diagnosed with the disease between 2004 and 2010.
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