Mri measurement of perineal and pelvic muscles as a novel imaging marker for hypogonadism

Abstract Introduction Low serum testosterone (T) in the presence of clinical symptoms of hypogonadism is essential in determining who may benefit from T replacement therapy. However, clinical symptoms associated with hypogonadism are non-specific and challenging to discriminate from other etiologies. While low bone mineral density is an objective primary end-organ effect of low testosterone, DEXA scans are not recommended by national guidelines due to poor sensitivity and specificity, and the limitation that these changes likely manifest over a prolonged period of time. Notably, prior studies have demonstrated that perineal ultrasound of the bulbocavernosus muscle (BCM) can be an effective surrogate to evaluate end-organ activity of hypogonadism. However, it is unclear if low BCM area is secondary to or rather correlated with hypogonadism, and longitudinal studies assessing men in both the eugonadal and hypogonadal state are lacking. Objective To report an initial experience with measuring the androgen-sensitive BCM, ischiocavernosus muscle (ICM), and levator ani muscles (LAM) on MRI in men before and after androgen deprivation therapy (ADT) as a novel imaging marker for end-organ effects of hypogonadism. Methods Data was collected from treatment-naive patients with intermediate or high-risk localized prostate cancer enrolled in a clinical trial involving six months of neoadjuvant treatment with goserelin and enzalutamide prior to prostatectomy. Patients underwent 3-Tesla multiparametric MRI of the prostate prior to treatment and again immediately prior to prostatectomy. An expert genitourinary trained radiologist retrospectively assessed MR images and measured width of the bilateral BCM, ICM, and LAM on coronal T2W MRI (Figure 1). Paired t-tests were performed to evaluate changes in muscle width before and after ADT. Linear regression was performed to evaluate the relationship between change in total testosterone levels and change in muscle width. The lower detection limit of testosterone was 20 ng/dL, and T less than 20 ng/dL was set to 0 for statistical analysis. Results 38 patients with pre- and post-treatment MRIs were identified with a median time between scans of 6.85 months. Median age at start of trial was 62.5 years (IQR: 58-69). 28/38 patients had documented AUA/IPSS and SHIM questionnaires with median scores of 8 and 19.5, respectively. Mean total testosterone prior to androgen deprivation was 289.5 ng/dL (SD= 121.7). 34/38 patients reached castrate level (T less than 20 ng/dL) after treatment completion, with mean testosterone 4.7 ng/dL (SD= 15.4). Muscle width was significantly reduced in all three muscle groups following ADT (Table 1). Linear regression found that decreases in testosterone significantly predicted decreases in combined perineal muscle (BCM + ICM) width (β = 0.0056, p = 0.032). Conclusions Decreases in testosterone to castrate levels led to significant and rapid decreases in sizes of both perineal and pelvic muscles. This shows initial plausibility in using an image-based approach to assess a short- to intermediate-term objective marker of end-organ effects of hypogonadism. Future prospective studies with larger samples and refinement of MRI sequences may lead to a useful clinical tool in the diagnosis and clinical workup of hypogonadism, and help clinicians better understand who would benefit from testosterone supplementation. Disclosure No