Transrectal ultrasound for monitoring murine orthotopic prostate tumor

BACKGROUND. The mouse orthotopic prostate tumor model has been recognized a s an ideal preclinical animal model simulating the anatomical and biologica l milieu of the prostate. In comparison with the subcutaneous tumor model, the only disadvantage of this model is the difficulty of chronological tumo r growth monitoring. We have applied recent endoluminal ultrasound technolo gy, transrectal ultrasonography (TRUS), to the monitoring of mouse orthotop ic prostate tumors. METHODS. A 6 Fr. 20 MHz catheter-based radial scan probe was used and TRUS was performed without any prior preparation including anesthesia. Orthotopi c tumors were initiated by inoculation of 5000 RM-9 cells into the dorsal p rostate of 12-week-old C57BL/6 male mice. The tumor growth was monitored by TRUS from day 3 to day 21. In addition, TRUS was performed to detect tumor growth suppression after intraperitoneal administration of cis-diamminedic hloroplatinum (CDDP). RESULTS. By ultrasound, tumors became detectable 7 days after tumor cell in oculation. TRUS images were clear and parallel to actual tumor growth. The tumor volume (X) calculated by TRUS correlated significantly with the actua l tumor weight (Y) measured at autopsy; Y = 101.653 + 1.174X (R = 0.930, P < 0.001). Similarly, tumor growth suppression induced by CDDP was clearly d etected by TRUS with reasonable accuracy. CONCLUSIONS. A high resolution TRUS allows simple and reliable monitoring o f in situ tumor growth and growth suppression, making the mouse orthotopic prostate tumor model more efficient. Prostate 47:118-124, 2001. (C) 2001 Wi ley-Liss, Inc.