Loss of skeletal muscle (SM) and gain of subcutaneous fat (SCF) are known side-effects of androgen-deprivation in treatment of prostate cancer. Scarce data is available concerning the effects of abiraterone/pred (ABI) on body composition and no published data regarding enzalutamide (ENZA). Our objective was to analyse the effects of ENZA on SM/SCF and to compare the results with ABI in patients with metastatic castration-resistant prostate-cancer (mCRPC).
54 patients starting ABI (n = 17) or ENZA (n = 37) at a single-centre between 2012 and 2018 were retrospectively identified. SM and SCF were assessed using CT-scans at baseline and after a median of 10.8 months on treatment. A deep learning image-segmentation software was used to quantify SM and SCF. In a subgroup of patients receiving ENZA within a trial, we investigated change of SM using serial timepoints.
Median time of treatment with ABI/ENZA was 14.6 months. A significant loss of SM compared to baseline was observed for ENZA (mean loss 5.2%, p<0.0001) and ABI (mean loss 3.0%, p = 0.02). SCF was not significantly altered. The effects of both drugs did not differ significantly. Loss of SM occurred early on during treatment with ENZA.
Treatment with ENZA seems to lead to a loss of SM which is comparable to that of ABI. Further evaluation in larger patient-cohorts is warranted. In routine care, counselling of patients about side effects of ABI/ENZA should include discussions about SM loss.

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