A Second Breast Cancer – Alcohol, Obesity, Smoking…..and Not Taking Your Medication

How do you prove that lifestyle factors can prevent breast cancer or breast cancer recurrence? The best evidence would come from interventional studies, studies comparing groups that make lifestyle changes with those that don’t.  Unfortunately, we just don’t have many of those studies.  What we do have, are a lot of studies looking at associations.  But you learn in stats 101 to be careful with these studies.  Association is not causation.

One of these association studies was published yesterday, in the online Journal of Clinical Oncology.  Investigators from the Fred Hutchinson Cancer Research Center found that developing a second breast cancer was  associated with obesity, regular intake of alcohol, and smoking.

The researchers compared weight and lifestyle habits between a group of 365 women who were diagnosed with breast cancer twice and a group of 726 matched controls with just one breast cancer diagnosis.  All patients had been originally diagnosed with an estrogen receptor positive breast cancer.

Being overweight at the original diagnosis, smoking, and drinking more than seven drinks a week were all associated with an increased risk for a second breast cancer.  Those who both smoked and drank regularly had a seven times greater risk of a second cancer, compared to those who did not smoke or drink.

The headline in the news today?   “Obesity, Alcohol Consumption, and Smoking, Increase Risk of Second Breast Cancer”  Ok, but what else?  What wasn’t reported?

The most  important factor.

Those who didn’t develop a second breast cancer?  They were  also much more likely to have been treated with hormonal therapy (p< .0001, for you statistics geeks).   Almost 40% who developed a second breast cancer were never given a hormonal treatment, and futhermore, less than 20% of ALL those in the study actually completed the recommended five years of treatment.  The real news to me seems to be the extremely low numbers of people who complete their treatment!

Bottom line?  Should those who have had estrogen receptor positive breast cancer aim for a healthy weight and healthy habits?  You bet.  But will avoiding that glass of wine or refusing dessert protect us from another breast cancer?  Probably not, and certainly not nearly as much as taking our hormonal medication.

News report http://www.scienceblog.com/cms/obesity-alcohol-consumption-and-smoking-increase-risk-second-breast-cancer-24932.html

Journal article  http://jco.ascopubs.org/cgi/content/abstract/JCO.2009.23.1597v1

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