Risk for Breast Cancer Recurrence Decreased by Lifestyle Changes

From Medscape Medical News
Roxanne Nelson

September 9, 2009 — Breast cancer survivors might be able to reduce their risk for contralateral breast cancer by making lifestyle modifications. A new study published online September 8 in the Journal of Clinical Oncology has found that obesity, alcohol use, and smoking all significantly increase the risk for second primary invasive contralateral breast cancer among breast cancer survivors.

Researchers from the Fred Hutchinson Cancer Research Center in Seattle, Washington, found that obese women had a 50% increased risk for contralateral breast cancer, and those who consumed 7 or more alcoholic drinks per week had a 90% increased risk. Survivors who currently smoked had a 120% increased risk of developing a second breast cancer.

The risk was particularly high in women who were current smokers and who consumed at least 1 alcoholic beverage a day. The authors found that this subgroup of women had a 7.2-fold (95% confidence interval [CI], 1.9 to 26.5) elevated risk for contralateral breast cancer.

Limited Data on Role of Lifestyle in Preventing Second Cancer

There is substantial evidence that modifiable lifestyle factors play a significant role in the risk for primary breast cancer. As recently reported by Medscape Oncology, an updated version of the American Institute for Cancer Research/World Cancer Research Fund's report, Food, Nutrition, Physical Activity, and the Prevention of Cancer: A Global Perspective, reaffirmed that factors such as maintaining a healthy weight, exercising regularly, and limiting consumption of alcoholic beverages can reduce the risk of developing breast cancer.

However, information on lifestyle factors and their role in preventing contralateral disease in survivors is more limited. The authors point out that although adjuvant hormone therapy can lower the risk by 47%, little is known about other factors that are within the patient's control.

Reducing the risk for a second cancer is of considerable concern, they note, because breast cancer survivors have a risk of developing a contralateral breast cancer that is 2 to 6 times greater than that of women in the general population developing a first breast cancer. Therefore, identifying potentially modifiable risk factors is of public-health relevance and of individual importance to breast cancer survivors, the authors note.

"But 1 issue in our study was that while some of the smokers stopped smoking, few of the drinkers changed their drinking habits, and few of the obese women lost weight, so we could not directly assess the impact that changing these habits had on reducing risk of a second breast cancer," lead author Christopher I. Li, MD, PhD, associate member of the Public Health Sciences Division at the Hutchinson Center, told Medscape Oncology.

"That said, the evidence regarding obesity and alcohol use and risk of a first breast cancer does suggest that reducing body weight and reducing alcohol consumption does lower risk of first breast cancer, so I would expect that changing these things could also reduce the risk of second breast cancer," he added.

Obesity, Alcohol Use, and Smoking Increase Risk

In this study, Dr. Li and colleagues evaluated the effect of obesity, alcohol consumption, and smoking on risk for second primary invasive contralateral breast cancer among breast cancer survivors.

The cohort consisted of 365 women who were diagnosed with an estrogen-receptor (ER)-positive first primary invasive breast cancer and a second primary contralateral invasive breast cancer, and 726 matched controls who were diagnosed with only an ER-positive first primary invasive breast cancer.

Information regarding obesity, alcohol use, and smoking was acquired from medical-record reviews and from interviews with the participants. The researchers then used conditional logistic regression to assess the association of these 3 factors and the risk for a second cancer.

They found that compared with women who had a body mass index (BMI) lower than 25.0 kg/m2, those with a BMI of 30.0 kg/m2 or above had a higher risk for contralateral breast cancer (odds ratio [OR], 1.4; 95% CI, 1.0 to 2.1).

The consumption of alcohol was also positively related to an increased risk for a second cancer (OR, 1.9; 95% CI, 1.1 to 3.2) when evaluated at both the first diagnosis of breast cancer and during the interval between first breast cancer diagnosis and reference date.

In similar fashion, current smokers had an elevated risk for contralateral breast cancer (OR, 2.2; 95% CI, 1.2 to 4.0) at first breast cancer diagnosis and at reference date, compared with women who had never smoked. The association between smoking and cancer risk did not vary by pack-years, the authors note. A small number of women were smokers at the time of their first diagnosis but quit by their reference date (14 patients and 29 control subjects), and this did not seem to influence the risk of developing a second breast cancer.

This observation suggests that recent smoking is the most relevant to risk, the authors note. "There were also too few women who were exsmokers and who started smoking again after their first breast cancer diagnosis for us to be able to assess this aspect," said Dr. Li.

Impact of Hormone Therapy Unclear

Despite having ER-positive primary cancers, 30% of the control women and 39.5% of the patients with contralateral disease were not treated with adjuvant hormone therapy. However, the researchers explain that this cohort included patients who received their first breast cancer diagnosis nearly 2 decades ago. At that time, the use of hormone therapy differed from what it is now, and as a result, fewer women received this type of treatment or for the amount of time needed for it to confer maximal clinical benefit.

But given the low rates of hormonal therapy use in this cohort, "it is reasonable to ask whether the relationship between weight and alcohol use seen in this study would be maintained in women with ER-positive tumors treated according to current adjuvant therapy guidelines," writes Jennifer A. Ligibel, MD, from the Dana-Farber Cancer Institute, Harvard Medical School, in Boston, Massachusetts, in an editorial.

"Thus, further work is needed to define the impact of modifiable factors on the risk of second primary breast cancers from modern observational data sets including women treated with modern hormonal therapy regimens," she notes.

The study was funded by a grant from the National Cancer Institute. The study authors and editorialist have disclosed no relevant financial relationships.

J Clin Oncol. Published online before print September 8, 2009.