This study found that being obese, smoking, and drinking alcohol all increase the risk of breast cancer being diagnosed a second time in women previously diagnosed with hormone-receptor-positive disease.
The researchers looked at the records of more than 1,000 women successfully treated for hormone-receptor-positive early-stage breast cancer. About 360 of the women were later diagnosed with a new breast cancer in the opposite breast (known as contralateral breast cancer). The researchers wanted to know if being obese, smoking, and regularly drinking alcohol contributed to the risk of developing a second breast cancer.
The risk of developing a second breast cancer was:
The researchers also found that women who drank regularly AND smoked were more than 7 times more likely to develop a second breast cancer compared to women who didn't smoke or drink regularly.
The women in this study were treated in the mid-1990s. At that time, hormonal therapy wasn't used as regularly as it is today. Since obesity and alcohol use may affect breast cancer risk by increasing hormone levels, it's possible that these factors may have less of an effect now because so many women take hormonal therapy medicine to reduce the risk of hormone-receptor-positive early-stage breast cancer coming back after surgery. Hormonal therapy reduces the risk of hormone-receptor-positive breast cancer coming back by blocking the effects or limiting the production of estrogen. Still, research shows a link between breast cancer risk and obesity, smoking, and drinking alcohol.
If you have been treated for early-stage breast cancer, try to do all you can to lower both your risk of the cancer coming back AND your risk of a new, second breast cancer. Along with the treatment plan you and your doctor choose, a healthy diet and lifestyle can help keep these risks as low as possible:
Visit the Breastcancer.org Lower Your Risk section to learn about diet and lifestyle options to keep your risk as low as it can be.
The tenuous link between lifestyle factors and breast cancer gained support from a study showing an increased risk of contralateral breast cancer related to obesity, smoking, and alcohol consumption.
The magnitude of the effect ranged from 40% for obesity to a twofold increased risk associated with moderate alcohol consumption and smoking, according to a report published online in the Journal of Clinical Oncology.
The combination of regular alcohol consumption and current smoking conferred a sevenfold increased risk of contralateral breast cancer.
The findings add to the limited data in the literature suggesting that modifiable factors play a role in the risk of a second primary cancer in the contralateral breast, Christopher I. Li, MD, PhD, of the Fred Hutchinson Cancer Research Center in Seattle, and colleagues concluded.
However, the study also raised questions that will require further study to answer, Jennifer A. Ligibel, MD, of the Dana-Farber Cancer Institute and Harvard Medical School in Boston, said in an accompanying editorial.
Obesity and alcohol consumption are associated with increased estrogen levels. Few patients in the case (39%) and control (30%) groups received hormonal therapy, possibly reflecting the cohort's enrollment in the mid-1990s, before the benefits of tamoxifen had been demonstrated conclusively.
"Due to a small number of events, [the authors] were not able to ascertain whether tamoxifen specifically lowered rates of contralateral beast cancer in obese women," said Ligibel.
"Data from randomized trials of weight loss and other behavioral interventions after breast cancer diagnosis is needed to determine whether changes in potentially modifiable risk factors in the years after breast cancer diagnosis could help lower risk of second primary breast cancer," she added.
Previous studies had yielded mixed results regarding associations between obesity, alcohol consumption, smoking, and the risk of breast cancer.
In an effort to clarify the associations, Li and colleagues studied 1,091 women diagnosed with primary estrogen receptor-positive breast cancer. Of those, 365 subsequently developed a second primary cancer in the contralateral breast.
By means of patients' medical records, investigators determined obesity (body mass index e30), alcohol use, and smoking status. They then examined associations between the three lifestyle factors and contralateral breast cancer, using logistic regression analysis.
The analysis demonstrated the following associations between the lifestyle factor and odds ratio for contralateral breast cancer:
"Our study results afford breast cancer survivors three ways to potentially reduce their risk of second cancers," Li said in a statement. "Stay at a normal weight, don't smoke, and drink in moderation."
The study was supported by a grant from the National Cancer Institute.
Neither Li and colleagues nor Ligibel reported potential conflicts of interest.
Primary source: Journal of Clinical Oncology Source reference: Li CI, et al "Relationship between potentially modifiable lifestyle factors and risk of second primary contralateral breast cancer among women diagnosed with estrogen receptor-positive invasive breast cancer" J Clin Oncol 2009; 27: DOI: 10.1200/JCO.2009.23.1597.Additional source: Journal of Clinical OncologySource reference: Ligibel JA "Could modification of lifestyle factors prevent second primary breast cancers?" J Clin Oncol 2009; 27: DOI: 10.1200/JCO.2009.24.4517.
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