Subcutaneous adipose tissue radiation attenuation is associated with chemotoxicity and survival in metastatic colorectal cancer

Background Skeletal muscle mass and radiation attenuation (RA) have been shown to be associated with chemotoxicity and survival in cancer patients. However, little is known about the clinical significance of adipose tissue RA, which has been hypothesized to be associated with tissue inflammation and insulin resistance. We investigated the association between adipose tissue RA, chemotoxicity, and survival in patients with metastatic colorectal cancer (mCRC) by performing a secondary analysis using data from a randomized controlled trial. Methods We included 104 mCRC patients treated with standard first-line chemotherapy. Using diagnostic abdominal computed tomography (CT) scans, we assessed height adjusted (cm2) area and RA of skeletal muscle (SM), visceral adipose tissue (VAT), and subcutaneous adipose tissue (SAT) at the third lumbar vertebra, and calculated SM index (SMI), VATI, and SATI as cm2/m2 based on stature. Associations between these body composition parameters and overall survival as well as chemotoxicity (NCI-CTCAE v 4.03) were evaluated using univariable and multivariable logistic and Cox regression analysis. Multivariable models evaluated body composition parameters, adjusted for age, sex, and significant clinically relevant covariates. Results Among the 104 patients in the cohort, 38 were female (36.5%). Mean age was 65.5 ± 9.5 years. 43 patients (41.3%) developed grade 3/4 toxicity. Pre-treatment SAT-RA was independently associated with grade 3/4 toxicities (OR = 0.78, 95% CI 0.62–0.98). Chemotherapy regimens and nutritional support were not associated with chemotoxicity. In the multivariable Cox analysis, SAT-RA (HR = 1.24, 95% CI 1.08–1.43) and SM-RA (HR = 0.74, 95% CI 0.61–0.90) were associated with shorter overall survival. Conclusion Higher SAT-RA and lower SM-RA at baseline were associated with shorter overall survival of patients with mCRC, and lower SAT-RA was associated with increased chemotoxicity. These body composition alterations should be investigated in future chemotherapy related studies.