Critical temperature for in vivo cryoablation of human prostate cancer in a xenograft model

Objectives To assess the in vivo sensitivity of human prostate cancer cells (PC3) to cryoablation and thus define the minimum temperature needed to prevent the recurrence of cancer after percutaneous transperineal radical prostatic cryoablation, Materials and methods Twenty-five male nu/nu mice were inoculated by a subcutaneous injection with 5 x 10(5) PC3 cells. After 3 weeks the tumours (mean area 60.4 mm(2), SEM 5.7) were frozen using a 3 mm cryotherapy probe (LCS 3000 Cryotech UK) to temperatures ranging from O degrees to -40 degrees C. Results No tumours recurred in seven mice which had tumours frozen to < -15 degrees C, There were eight recurrences in 15 mice which had tumours frozen to between 0 degrees and -15 degrees C, and all were confirmed histologically. Conclusions The minimum temperature required to prevent recurrence of tumours from human prostate cancer cells was < -15 degrees C in this in vivo mouse model.