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Obesity linked to poorer outcomes in HR-positive breast cancer
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Obesity was associated with inferior outcomes in patients with hormone receptor-positive operable breast cancer who were treated with standard chemohormonal therapy, according to study results.
Women who are obese when they are diagnosed with breast cancer have an increased risk of dying prematurely compared with women of normal weight.
In addition, prior studies have indicated that obese patients with lymph node-negative, ER-positive breast cancer who were treated with tamoxifen had increased rates of contralateral breast cancer, second primary cancers and other noncancer-related deaths.
Joseph Sparano
In this study, Joseph Sparano, MD, of the Albert Einstein College of Medicine’s Montefiore Medical Center, in Bronx, N.Y., and colleagues compared outcomes of 6,885 women with stage I to stage III breast cancer, assessing the role of chemotherapy or endocrine therapy regimens.
BMI data at the time of enrollment in the trial — after surgery but before initiation of chemotherapy or endocrine therapy — were available for 4,770 patients. Of them, 1,745 (36.6%) were obese, 1,540 (32.3%) were overweight, 1,447 (30.3%) had a normal BMI, and 38 (0.8%) were underweight.
Women who were classified as obese (BMI ≥30) and overweight (BMI 25-29.9) who had hormone receptor-positive/HER-2/neu-negative disease experienced poorer DFS (P=.0006) and OS (P=.0007), according to study findings. Researchers did not observe this association in patients with triple-negative disease or HER-2–positive disease.
“We found that obesity at diagnosis of breast cancer is associated with about a 30% higher risk of recurrence and a nearly 50% higher risk of death despite optimal treatment,” Sparano said in a press release. “Treatment strategies aimed at interfering with hormonal changes and inflammation caused by obesity may help reduce the risk of recurrence.”
Obese and overweight patients had larger primary tumors, were more likely to require breast-conserving surgery and exhibited different distribution of nodal metastases, according to the researchers. There were no significant differences in the biologic characteristics of the tumor.
“The results of this analysis clearly establish a relation between higher BMI at the time of breast cancer diagnosis and higher risk of recurrence and death, specifically in hormone receptor-positive, HER-2–negative disease, which accounts for about two-thirds of all breast cancers,” the researchers wrote. “What remains uncertain, however, is whether dietary and lifestyle interventions resulting in weight loss after a breast cancer diagnosis could substantially reduce the risk of recurrence, and also perhaps provide secondary benefits in reducing cardiovascular morbidity and mortality.”
Disclosure: The researchers report no relevant financial disclosures.
Perspective
Back to TopDebasish 'Debu' Tripathy, MD
This report by Sparano and colleagues highlights the adverse relationship that obesity has on cancer outcomes – a finding that has been reported before, but is now shown very clearly in a well-controlled cohort of patients treated on specific chemotherapy protocols. This analysis, confined to hormone receptor-positive cases, illustrates the relationship between metabolic and hormonal pathways that could be potentially exploited for therapeutic gain.
Others argue that obesity may be associated with higher recurrence but is not necessarily a driver. However, the Women’s Intervention Nutrition Study (WINS) showed that a low fat diet that caused weight loss led to fewer recurrences in a controlled study, supporting a causal relationship. However, compliance with such a diet and weight loss in general is problematic. A pharmacological approach is currently being tested in a large prospective trial (MA.32) randomizing patients to placebo or metformin, an oral hypoglycemic that lowers glucose and insulin. As we await the results of this trial, we should at least be uniformly recommending that cancer patients maintain an ideal body weight and a physical exercise regimen – an approach endorsed by the American Cancer Society, ASCO and others.
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