Castration Levels of Testosterone Results in Atrophy of Androgen-sensitive Perineal Muscles: A Potential Biomarker...

To evaluate MRI-based measurements of androgen-sensitive perineal/pelvic muscles in men with prostate cancer before and after androgen deprivation therapy (ADT) as a novel imaging marker for end-organ effects of hypogonadism. Diagnosing hypogonadism or testosterone deficiency (TD) requires both low serum testosterone and clinical symptoms, such as erectile dysfunction and reduced libido. However, the non-specific nature of many TD symptoms makes it challenging to initiate therapy. Objective markers of TD help to better identify patients who may benefit from testosterone supplementation; however, current markers, such as low bone mineral density, lack sensitivity. Previous studies suggest that decreased bulbocavernosus-muscle (BCM) thickness may be associated with TD, although it remains unclear if this is a correlative relationship.

Data were prospectively collected for patients with intermediate/high-risk localized prostate cancer enrolled in a phase II trial (NCT02430480). Patients received ADT before prostatectomy and underwent prostate MRI pre-/post-ADT. BCM, ischiocavernosus-muscle (ICM), and levator-ani-muscle (LAM) measurements were made using T2W-MRI. Paired t-tests evaluated changes in BCM/ICM/LAM width, and linear regression analyses evaluated relationships between changes in testosterone and muscle width.

Thirty-eight consecutive patients with pre-/post-ADT MRIs were analyzed. Baseline testosterone was 286.5ng/dL, and 36/38 patients had post-ADT testosterone <50ng/dL. Pre-ADT and post-ADT measurements of the bilateral BCM/ICM/LAM width were 7.16mm/7.95mm/5.53mm and 5.68mm/6.71mm/4.89mm, respectively (P <.001). Decreases in testosterone predicted reduction in combined perineal muscle (BCM+ICM) width (P = .032).

Androgen deprivation led to significant and relatively rapid decreases in BCM/ICM/LAM thickness. This objective biomarker of low testosterone states may help identify patients who will potentially benefit from testosterone replacement.