According to new research published in JAMA Oncology, measurements of muscle mass and adiposity drawn from the CT scans of patients with breast cancer predicted their survival better than calculations of BMI (body mass index).
First author Bette Caan of Kaiser Permanente in Oakland noted that there have been several studies conducted that have identified a correlation between body composition measures on CT and cancer survival. Quite a few of these studies also concluded that these measures may provide better prognostic information than traditional BMI.
Caan and her colleagues took a step further, applying this concept specifically for the assessment of breast cancer. During the study, muscle mass, total adipose tissues, and various other body composition measures were all evaluated on the CT scans of 3,241 women diagnosed with stage II or III nonmetastatic breast cancer.
The women used for the study were all patients at Kaiser Permanente of Northern California and Dana-Farber Cancer Institute in Boston, and underwent CT scanning at the time of cancer diagnosis. There were a total of 3,241 women, with a median age of 54 years, and 1,086 of them had low muscle mass (sarcopenia).
After analyzing the data, it was discovered that patients with low muscle mass had a 41% greater risk of dying compared to those without low muscle mass. Even after adjusting for age, BMI, cancer stage, and emergency status, this relationship remained. It was also found that patients with a high total adipose tissue had much higher overall mortality (or hazard ratio), than those with low total adipose tissue, whether or not they had low muscle mass.
Because of these findings, the overall survival rate of patients who had both low muscle mass and high total adipose tissue was lower than patients without these conditions. The difference was statistically different. (p < 0.001)
CT-based muscle mass and fat content measurements demonstrated a stronger association with mortality than even high BMI, the study found. The standard measure for obesity (a BMI of at least 30), turned out not to have a statistically significant association with overall mortality and did not identify patients at risk of death due to body composition.
The results of the study have shown that building and maintaining muscle mass is incredibly important for breast cancer survivors.
“Future studies should aim to evaluate body composition effects by tumor subtype and by race/ethnicity, as well as examine in more detail the confounding and/or modifying effects of treatment and its effect on changes in body composition during the follow-up period,” says Dr. Elisa Bandera, PhD, from the Cancer Prevention Institute of California in an invited commentary.