medwireNews: Approximately one-third of women with nonmetastatic breast cancer present with sarcopenia, which is associated with a significantly increased risk for death, study findings indicate.
Furthermore, “muscle and fat mass assessed from clinically acquired CT [computed tomography] scans are more strongly associated with survival than BMI [body mass index], suggesting these would be more useful in identifying women at risk of poor survival due to adiposity,” Bette Caan (Kaiser Permanente, Oakland, California, USA) and co-authors write in JAMA Oncology.
They add: “These prognostic measures can be easily integrated into routine clinical care using new software to generate highly accurate measures of body composition from clinically collected CT scans.”
The observational study included 3241 women (median age 54 years) with stage II or III breast cancer who were followed-up for a median of 6 years. During this time there were 619 deaths.
CT scans, taken within 6 months of diagnosis and before chemotherapy or radiation, revealed that 34% of patients presented with sarcopenia (low skeletal muscle mass) and 37% had low muscle radiodensity, which is an indicator of poor muscle quality.
After adjustment for sociodemographic factors, tumor characteristics, treatment, BMI, and other measures of body composition, women with sarcopenia had a significant 41% increased risk for overall mortality compared with those without sarcopenia.
Increased adiposity was also associated with increased mortality rates, with women in the highest tertile of total adiposity having a significant 35% higher risk for death than those in the lowest tertile.
When the researchers analyzed sarcopenia and total adiposity together they found that patients with sarcopenia and total adiposity in the top tertile had the greatest risk for death, at a hazard ratio of 1.89, compared with nonsarcopenic patients with low total adiposity. They say this “can be attributed to an additive effect of the 2 risk factors.”
Importantly, the associations were consistent across strata of age, BMI, cancer stage, and estrogen receptor status.
By contrast, neither BMI nor skeletal muscle density were significantly associated with overall mortality.
And the team notes that only 18% of overweight patients (BMI 25–30 kg/m2), along with 73% of those with class I obesity (BMI 30–35 kg/m2), were classified into the highest tertile of total adiposity.
This “could explain why prior studies did not always find significant associations between BMI and survival for women with BMI less than 35,” Caan et al remark.
The authors conclude: “Both muscle and adiposity represent modifiable risk factors in patients with breast cancer.”
They add: “In the era of precision medicine, the direct measurement of muscle and adiposity will help to guide treatment plans and interventions to optimize survival outcomes.”
In a comment that accompanies the study, Elisa Bandera (State University of New Jersey, New Brunswick, USA) and Esther John (Stanford University School of Medicine, Fremont, California, USA) describe the findings as “important” because they clarify “the role of body composition in survival after a breast cancer diagnosis.”
The commentators add that the results “are an important reminder that weight loss and/or weight control programs must always incorporate physical activity with the goal of not just reducing adiposity, but maintaining and increasing muscle mass, which would not only reduce the risk of death, but also help improve quality of life after a cancer diagnosis.”
By Laura Cowen
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