Background: Despite global testosterone deprivation and loss of lean mass by DXA of 3%, androgen deprivation therapy (ADT) for prostate cancer leads to a relatively large selective loss of leg muscle function during walking, predominantly affecting iliopsoas, quadriceps and soleus (1). We hypothesized that this selective loss of muscle function would be reflected in greater decreases in loss of corresponding muscle volumes.
Methods: We conducted a prospective case-control study involving 31 men newly commencing ADT and 31 age- and radiotherapy-matched prostate cancer controls. Leg muscle volume was measured using MRI and quantitated using Slice-O-Matic software at 0 and 12 months. Muscle volume (L) was quantitated from iliopsoas, quadriceps, gluteus maximus, gluteus medius and calf muscles which are primary muscles involved in walking. The intraobserver CV was <1%. Median regression analysis was performed to assess change over time by group, adjusted for baseline values. Medians [95% CI] are presented.
Results: Data was available for 21 men in the ADT group and 21 controls at 12 months. Total testosterone levels decreased from 14.1 to 0.4nmol/L in the ADT group (p<0.001) but were stable in controls over 12 months. Compared with controls, the ADT group had greater reductions in gluteus maximus by 8% of the initial median value (-0.057 L [-0.098, -0.017], p=0.006) and quadriceps by 4% (-0.061 L [-0.121, -0.002], p=0.044). No significant between group differences were observed for the gluteus medius muscle (-0.008L [-0.018, 0.001], p=0.072), iliopsoas (-0.005 L [-0.011, 0.000], p=0.068) or calf (-0.003 L [-0.030, 0.024], p=0.848).
Conclusion: While inferences are constrained by the small sample size, we find that similar to muscle function, ADT leads to a selective loss of leg muscle volume. However, loss of muscle volume is not always paralleled by functional deficits, suggesting that factors other than muscle mass contribute to androgen mediated functional performance.