New research shows risk of breast cancer is greater when women smoke before having their first child

Research presented yesterday at the World Cancer Congress shows that one in eleven breast cancer cases in mothers can be prevented if women do not smoke before having their first child.

With the majority of female smokers starting before their first pregnancy, the findings support the view that women can reduce their risk of breast cancer if they quit smoking now rather than waiting until they decide to have children.

The key research¹ highlights include:

• Of 137,412 Norwegian women (90% mothers), aged 34-70, followed for 12 years, 3,157 developed breast cancer and one in 11 of these cases could have been prevented if these women did not start smoking before their first birth
• Immature breast tissue is more susceptible to carcinogens (that contain cancer-causing chemicals) from tobacco smoke than breast tissue that has matured completely, which happens after a woman has given birth and has breast-fed

The lead-author of the research is Dr Inger Gram, a professor at University of Tromsø, Norway.

Smoking and breast cancer

More than 150 scientific papers have been published on smoking and risk of breast cancer. However, as yet smoking is not an established risk factor for breast cancer with disagreement between experts on this topic. While the Canadian Expert Panel on Tobacco Smoke and Breast Cancer Risk concluded in 2009 that the relationship between smoking and breast cancer was consistent with causality, the Monograph from the International Agency for Research on Cancer in 2012 classified cigarette smoking as possibly carcinogenic to the human breast and the most recent US Surgeon General report published this year concludes that the evidence is suggestive, but not sufficient to establish a causal relationship between tobacco smoke and breast cancer.

Globally, tobacco use among women is rising while the age at which they start daily smoking is decreasing.