Women who are at increased risk of breast cancer may further increase their risk if they smoke. Smoking was also linked with an increased risk of lung and colon cancers. These findings will be presented at the 2011 annual meeting of the American Society of Clinical Oncology.
Evidence continues to mount of an association between lifestyle factors and health. Commonly investigated behaviors include physical activity, diet, smoking, and alcohol consumption.
To assess the relationship between these factors and risk of several common cancers in women, researchers evaluated information from the National Surgical Adjuvant Breast and Bowel Project Breast Cancer Prevention Trial. The study enrolled more than 13,000 women who were at increased risk of breast cancer as a result of their personal or family medical history. Women reported their cigarette-smoking, alcohol use, and physical activity.
At the beginning of the study, 13% of women reported current smoking. Alcohol use was reported as follows: 21% reported no daily drinking, 66% reported drinking up to one drink per day, and 13% reported drinking more than one drink per day.
- Women who smoked had an increased risk of invasive breast cancer compared with women who didn’t smoke. This risk increased with more years of smoking: women who smoked for at least 30 years had a 60% higher risk than non-smokers, and women who smoked between 15 and 35 years had a 34% higher risk.
- Risk of colon cancer was also higher among women who smoked than non-smokers—four times higher among those who smoked for more than 35 years and 7% higher among those who smoked for 15 to 35 years.
- Lung cancer risk was significantly higher among women who smoked. Compared with never-smokers, risk was 30 times higher for those who smoked more than one pack of cigarettes per day for over 35 years. Those who smoked less than one pack a day for more than 35 years had a 13-fold increased risk.
- Unlike many previous studies, this study did not find an increased risk of breast cancer associated with alcohol consumption. Moderate alcohol consumption (up to one drink per day) was associated with a reduction in risk of colon cancer of 60% compared with no consumption. The researchers note that the absence of an association between alcohol consumption and increased cancer risk in these findings could be due to a smaller number of heavy drinkers enrolled in this study compared with others.
- A low level of physical activity did not appear to increase the risk of breast, colon, or lung cancer, but it did appear to increase the risk of endometrial cancer by 70%. According to the researchers, this may be due to association between low physical activity and obesity, as obesity is another risk factor for endometrial cancer.
For women who are already at increased risk of breast cancer, this study highlights the importance of avoiding tobacco smoke. Smoking—particularly long-term smoking—was linked with an increased risk of breast cancer, colon cancer, and lung cancer. “We’re seeing again that smoking cessation is one of the most effective tools we have for reducing risk of many cancers,” said one researcher on the study.
Reference: Land SR, Christian N, Wickerham DL, et al. Cigarette smoking, fitness, and alcohol use as predictors of cancer outcomes among women in the National Surgical Adjuvant Breast and Bowel Project (NSABP) Breast Cancer Prevention Trial (BCPT).
To be presented at the 47th Annual Meeting of the American Society of Clinical Oncology (ASCO), Chicago, IL, 3-7, 2011. Abstract 1505.