Carolyn McAnlis, Dietitian and Pink Hope Outreach Ambassador discusses smoking and breast cancer in this blog post.
It’s well known that smoking cigarettes directly causes lung cancer, and it can also affect our risk of other cancers and a person’s general health. But can it affect the risk of breast cancer? Let’s examine the evidence of smoking’s relationship with breast cancer.
Harvard Medical School (US) conducted a review of research studies in 2011 and found that women who were regular smokers for any length of time had a 6 per cent higher risk of developing breast cancer compared to women who never smoked. Those who smoked larger quantities over time, measured as one pack per day for 30 years or more, had a 28 per cent higher risk of breast cancer than women with no history of smoking.
It’s unclear whether this is a direct causal relationship, or whether it is the assumption that smokers are more likely to partake in other unhealthy lifestyle behaviours like higher intake of alcohol, which increases the risk of cancers such as breast cancer risk on its own.
In thinking about breast cancer one of the researchers, Karin Michels, PhD, explained that she “would not put [smoking] on the list of important risk factors, [but] when you look at the subgroup of heavy-duty smokers who start early and smoke for a long time, that’s more serious.”
Many previous studies have tested smoking’s link to breast cancer; however, results have been inconclusive, depending on when subjects first began smoking as well as the duration of the habit.
What has been demonstrated, however, is the importance of not smoking in the time surrounding surgery or treatment like chemotherapy or radiotherapy. Patients are instructed to quit smoking before surgery, but may not understand why it is so important. Smoking causes constriction of the blood vessels, which means that blood flow is reduced, making it harder to deliver adequate amounts of oxygen to tissue in the body. This is especially critical for flap surgeries, where blood supply to the transplanted tissue is vital to maintain the health of the flap in order to have a successful result. Quitting smoking is generally advised at least 6 weeks prior to surgery or treatment.
Aside from slow or poor wound healing after surgery, smoking can increase other complications. Smoking worsens the side effects of harsh treatments required for fighting cancer, like causing further damage to lungs after radiation to the chest or increasing the risk of blood clots.
The probability of death from breast cancer increases with smoking. A study in Japan examined the survival of 800 women with breast cancer, and found those who had smoked for “more than two decades had at least triple the odds of dying of any cause, or from breast cancer in particular, compared with women who never used cigarettes.” This is not a direct link between smoking and developing breast cancer, but instead a link between breast cancer diagnosis and chance of survival.
Aside from the potential slight increased risk of breast cancer that results from a cigarette habit, more important are the detrimental effects that smoking can have on treatment outcomes and overall survival. Quitting smoking is one of the best ways that women can improve their survival rates and outcomes of breast cancer treatment.