P295 - CT VS. DXA FOR TRACKING MUSCLE LOSS DURING CHEMOTHERAPY: ARE LONGITUDINAL CT ESTIMATES RELIABLE?

P295

CT VS. DXA FOR TRACKING MUSCLE LOSS DURING CHEMOTHERAPY: ARE LONGITUDINAL CT ESTIMATES RELIABLE?

J. Bennett¹, C. Prado^2,*

¹University of Hawaii Cancer Center, Honolulu, United States, ²University of Alberta, Edmonton, Canada

Rationale: Accurate assessment of body composition is essential in cancer care, as changes in fat-free mass (FFM) reflect nutritional status, physical activity, and disease progression. In clinical oncology, body composition is often estimated using opportunistic computed tomography (CT) scans, yet the validity of CT for tracking longitudinal changes in FFM remains uncertain.

Methods: In the Protein Recommendations to Increase Muscle (PRIMe) randomized control trial, adults with stage II–IV colorectal cancer undergoing chemotherapy were assessed for the effects of increased dietary protein on muscle mass over 12w. Whole-body dual-energy X-ray absorptiometry (DXA) and opportunistically collected CT-based cross-sectional muscle area at the L3 vertebra were obtained pre- and post-intervention. Participants with DXA and CT scans within 30d of each timepoint were included. CT muscle area was converted to whole-body FFM using a validated equation.¹

Results: Among 16 participants, mean change in FFM was +0.02 ± 2.73 kg by DXA and –0.37 ± 3.92 kg by CT. In 3 participants (18.8%), DXA and CT indicated changes in opposite directions. The largest individual discrepancy was 8.11 kg (+1.96 kg by DXA, –6.15 kg by CT). Fourteen participants (87.5%) had >1 kg difference, and nine (56.3%) had >2 kg difference between DXA and CT estimates of change.

Image:

Conclusion: Estimates of longitudinal FFM change derived from serial CT scans diverge significantly from DXA measurements, with large differences in direction and magnitude. These findings raise concern about relying solely on opportunistic CT for monitoring nutritional status during cancer treatment. In clinical settings where nutrition interventions are guided by changes in body composition, validated whole-body methods like DXA should be prioritized to ensure accurate assessment and appropriate care planning.

References: ¹Mourtzakis, M. (2008). App Physiol Nutr Metab, 33(5), 997-1006.

Disclosure of Interest: J. Bennett: None declared, C. Prado Grant / Research Support from: Campus Alberta Innovation Program funding from the Government of Alberta