Spinal multiparametric MRI and DEXA changes over time in men with prostate cancer treated with androgen deprivation therapy: a potential imaging biomarker of treatment toxicity

Objectives: To explore changes in bone mineral density (BMD) measured by DEXA and MRS fat fraction (FF), Dixon FF, and ADC in lower spinal vertebral bodies in men with prostate cancer treated with androgen deprivation therapy (ADT). Methods: Twenty-eight men were enrolled onto a clinical trial. All received ADT. DEXA imaging was performed at baseline and 12 months. L-spine MRI was done at baseline and 6 months. Results: The number of patients who underwent DEXA, Dixon, ADC, and MRS at baseline/follow-up were 28/27, 28/26, 28/26, and 22/20. An increase in FF was observed from T11 to S2 (average 1 %/vertebra). There was a positive correlation between baseline MRS FF and Dixon FF (r = 0.85, p < 0.0001) and a negative correlation between MRS FF and ADC (r = -0.56, p = 0.036). Over 6 months, MRS FF increased by a median of 25 % in relative values (p = 0.0003), Dixon FF increased (p < 0.0001) and ADC values decreased (p = 0.0014). Men with >5 % BMD loss after 1 year had triple the percentage increase in MRS FF at 6 months (61.1 % vs. 20.9 %, p = 0.19). Conclusions: Changes are observed on L-spine MRI after 6 months of ADT. Further investigation is warranted of MRS change as a potential predictive biomarker for later BMD loss.