mTOR Inhibitor Therapy for Tuberous Sclerosis Complex: Longitudinal Study of Muscle Mass Determined by Abdominal Cross-sectional Imaging with CT and MRI.

Purpose: To determine the effect of chronic mammalian target of rapamycin (mTOR) inhibition on skeletal muscle mass in patients with tuberous sclerosis complex (TSC).

Materials And Methods: In this retrospective study, patients with TSC who were taking mTOR inhibitors and who underwent at least two abdominal CT or MRI examinations between 2005 and 2017 were included ( = 24; 14 males; mean age, 14.5 years ± 7.8 [standard deviation] at first examination). One reviewer drew regions of interest around psoas muscles at L3 to measure cross-sectional area. Multiple linear mixed-effect modeling was performed to evaluate the association between muscle mass and the covariates over time.

Results: The 24 patients underwent a total of 129 abdominal CT or MRI examinations. Median duration of mTOR inhibition at last examination was 106 months (range, 1310-3717 days). There was no significant association between the duration of mTOR inhibitor therapy and psoas muscle area on multiple linear mixed-effect modeling ( = .055); however, patient height and height squared were significant predictors of psoas area ( = .014 and < .0001, respectively).

Conclusion: Duration of mTOR inhibition in TSC was not significantly associated with a decrease in psoas muscle area, suggesting that chronic mTOR inhibition is not associated with sarcopenia. CT, MR-Imaging, Pediatrics© RSNA, 2020.