Sorafenib-induced Prostate Volume Reduction, a New Adverse Effect Detected by Imaging: A Pilot Study.

Background: Sorafenib has been used in the treatment of advanced hepatocellular carcinoma (HCC) and renal cell carcinoma (RCC). Sorafenib-associated organ reduction have been reported on imaging, such as thyroid, pancreas and muscle, but there has been no research on prostate volume reduction (PVR). Methods: We retrospectively analyzed 26 patients (twenty with HCC and six patients with RCC) who underwent sorafenib therapy for 31 to 1225 days (median, 100 days). PVR was estimated by two independent readers using CT volumetry. Results: The sum of all prostate volumes measured by reader 1 was 24.2 +/- 13.8 cm(3) on the baseline CT and 20.4 +/- 10.6 cm(3) on the follow-up CT (p < 0.001), and that measured by reader 2 was 22.3 +/- 13.9 cm(3) on the baseline CT and 19.2 +/- 10.6 cm(3) on the follow-up CT (p < 0.001). The concordance correlation coefficient for the prostate volume measured by the two readers was 0.95 on the baseline CT scans and 0.94 on the follow-up CT scans. Sorafenib-associated PVR demonstrated slight dependence to the exposure time (r = -0.23). One patient with benign prostatic hyperplasia (BPH) showed PVR (from 80.4 to 61.5 cm(3) [reader 1]; 83.4 to 61.6 cm(3) [reader 2]) after sorafenib administration. Sorafenib-associated PVR occurred in patients both with and without underlying liver dysfunction with relative prostate volume changes of 86.7 +/- 12.0% and 85.0 +/- 9.0%, respectively. Conclusion: Our study demonstrated significant PVR with sorafenib treatment in patients regardless of the presence of BPH and underlying liver dysfunction.