Inclusion criteria for cancer cachexia clinical trials: CT-defined skeletal muscle loss versus body weight loss.

Abstract

67 Background: Cancer cachexia is defined by skeletal muscle loss, with or without fat loss (Fearon et al 2011); however, inclusion criteria for cachexia clinical trials requires a defined weight loss over time rather than muscle loss. We hypothesized that cross sectional imaging may reveal the presence of cachexia otherwise obscured by fat mass changes. Methods: A retrospective analysis of longitudinal CT scans was performed in metastatic colorectal cancer (mCRC) patients screened for a cancer cachexia trial, which required ≥5% weight loss in the prior 6 mos. De-identified CT images were analyzed for total muscle, subcutaneous, and visceral fat cross-sectional areas (cm2) at the 3rd lumbar vertebra at baseline and up to 12 mos prior (Lieffers et al 2009). Logistic regression was used to test differences between patients with <5% vs ≥5% weight loss. Random intercept regression was used to evaluate significant trends in CT measures over time. Results: 42 mCRC patients were screened and 3(7%) enrolled. Patients were excluded for comorbidity/contraindication 14 (33%), excessive [>20%] weight loss 4 (9.5%), and insufficient [<5%] weight loss 19 (45%). For the <5% weight loss subset, there was a mean of 6.7 CT scans (SD=2.67) and of 9% (SD=5.4, min=0%, 25th percentile=4.9%) mean max muscle loss. Notably this group was simultaneously losing muscle (p=0.002) and gaining visceral adipose (p=0.007). For the ≥5% weight loss subset, there was a mean of 7.5 CT scans (SD=4.5) and 20% (SD=10.0, min=5.2%, 25th percentile =10.6) mean max muscle loss. Greater max muscle loss increased the odds of being in the ≥5% weight loss subset (OR=1.19, 95% CI: 1.06,1.33). This group also had a significant decrease in visceral adipose over time (p<0.001). Redefined inclusion criteria of ≥5% muscle loss would have included 14 of the 19 patients excluded because of <5% weight loss. Conclusions: Defining cancer cachexia as weight loss over time may be limited as it does not capture body composition changes and hinders trial accrual. Cross-sectional CT body composition analysis may improve early detection of muscle loss and improve trial accrual.