Three recent studies explored how smoking is related to certain breast and lung cancer risks. In the first study, postmenopausal women who were current or former smokers were found to have a 16% higher risk of developing breast cancer than never-smokers.1 The study also found that women who had extensive exposure to passive smoking, either as children or adults, had an excess risk of developing breast cancer. Although previous studies have indicated a link between smoking and breast cancer, passive smoking risk remains controversial. Researchers, led byJuhua Luo, MD, of West Virginia University in Morgantown, and Karen Margolis, MD, of Health-Partners Research Foundation in Minneapolis, Minnesota, used data from the 1993-1998 Women's Health Initiative Observational Study to determine links between smoking, passive smoking, and breast cancer They analyzed data from nearly 80,000 women between the ages of 50 and 79 years across 40 clinical centers nationwide, identifying a total of 3250 cases of invasive breast cancer diagnosed over 10 years. Participants were asked a variety of questions, including whether they had ever smoked, at what age they began smoking, how many cigarettes they smoked each day, and at what age they quit smoking. They also were asked if they had lived in smoking households as children or adults and whether they had worked in smoking environments. Researchers found that smokers had a 16% increased risk of developing breast cancer after menopause; former smokers had a 9% increased risk. Those women who had smoked for 50 years or more had the highest risk compared with lifetime nonsmokers. Women who started smoking as teenagers also had a particularly high risk. The increased risk continued for 20 years after a person had stopped smoking. Nonsmoking women who had been exposed to extensive passive smoking had a 32% excess risk of breast cancer “Extensive” was defined as more than 10 years' exposure in childhood, more than 20 years' exposure as an adult at home, and more than 10 years' exposure as an adult at work. However, because their analysis of secondhand smoke was limited to the most extensive passive smoking category, the authors say more research is needed to confirm these findings. In another study by Kenneth Piazza, MD, MPH, and Andrew Hyland, PhD, at Roswell Park Cancer Institute in Buffalo, New York, smoke free homes and workplaces were linked to reductions in breast cancer incidence and mortality rates.2 The study found a statistically significant decrease in breast cancer mortality, particularly among younger premenopausal women, as the number of smoke- free homes and workplaces increased. An estimated 20% of the change in breast cancer mortality rates was due to changes in smoke-free home and workplace policies. Similar to the first group of researchers, Drs. Piazza and Hyland cited the lack of definitive evidence regarding passive smoke and risk of breast cancer However, the study also found that states with higher percentages of women working and living in smoke-free environments had lower breast cancer rates. In a third study, researchers found that many longtime smokers quit spontaneously shortly before their lung cancer was diagnosed.3 As a result, they speculate that sudden smoking cessation may be a symptom of lung cancer The study found that most patients who quit did so before noticing any cancer symptoms. They also often quit with no difficulty, despite having tried to quit unsuccessfully in the past, notes lead author Barbara Campling, MD, a medical oncologist at Thomas Jefferson University in Philadelphia, Pennsylvania. Researchers interviewed 115 lung cancer patients from the Philadelphia Veterans Affairs Medical Center, all of whom had been smokers. Of these, 55 patients (48%) had quit smoking before diagnosis and only 6 (11%) of these patients had experienced symptoms before they quit. The patients who quit were as dependent on nicotine as those who continued to smoke, yet 31% said they quit without difficulty. Investigators compared these results with those found in patients with prostate cancer and heart attack survivors. In the patients with lung cancer, the median time elapsed between quitting smoking and lung cancer diagnosis was 2.7 years. The interval between quitting and the event was 24.3 years for patients with prostate cancer and 10 years for heart attack survivors. Dr. Campling and colleagues speculated that smoking cessation may be caused by tumor secretion of a substance that interferes with nicotine addiction. She cautions that these results should not be misinterpreted to suggest that heavy smokers should continue smoking; they still should be strongly encouraged to quit.
Read full abstract