Smoking Increases Postmenopausal Breast Cancer Risk
Posted Mar 02 2011 10:29am
As I have indicated in previous blogs , smoking has been linked to breast cancer in many studies. In fact, studies have suggested that smoking increases the risk for breast cancer recurrence, decreases breast cancer survival, and that nicotine induces breast cancer development.
An extensive, newly published breast cancer study examined smoking characteristics and their possible link to breast cancer risk in postmenopausal women ( free to download ). For this study, data on smoking habits, exposure to secondhand smoke, and breast cancer incidence were examined in nearly 80,000 women who took part in the Women's Health Initiative Observational Study from 1993 - 1998. Of these postmenopausal women, 3,520 women were diagnosed with invasive breast cancer. Analysis of the relationships between breast cancer incidence and smoking characteristics showed
Compared to lifetime non-smokers, current smokers had a 16% increased chance of developing breast cancer overall, while former smokers had 9% increased breast cancer risk.
Breast cancer risk increased with the number of cigarettes smoked each day. Breast cancer risk increased by 11% with 5 - 14 cigarettes per day and by 14% with 15 - 24 cigarettes per day compared to only 5% increased breast cancer risk with less then 5 cigarettes per day.
Similarly, the longer the women smoked, the greater their risk for developing breast cancer. Compared to non-smokers, women who smoked for more than 30 years had about a 15-20% increased breast cancer risk and women who smoked for more than 50 years had a 35% increased breast cancer risk.
Breast cancer risk was also linked to a woman's age when she started smoking. Breast cancer risk was greater in postmenopausal women who started smoking before 25 years of age and particularly in those who started smoking before 20 years of age.
Breast cancer risk decreased with the amount of time since quitting. Breast cancer risk returned to near normal levels 20 years after quitting smoking.
Exposure to secondhand smoke was only significantly linked to an increased breast cancer risk (32%), when exposure was extensive.
While this is clearly not the first study to link tobacco use to an increased risk for breast cancer, this is one of the largest studies to date that links breast cancer incidence to various smoking characteristics. The results of this study are important and confirm that smoking increases breast cancer risk. Postmenopausal breast cancer risk was greatest among women who started smoking at a young age, smoked for more than 30 years, and who smoked more than 5 cigarettes per day. Fortunately, the results of this study indicated that kicking the smoking habit can reduce a woman's breast cancer risk over time. Since it appears to take 20 years or more to reduce breast cancer risk to non-smoker levels, quitting as early as possible is the best approach.