CRYOABLATION OF HUMAN COLORECTAL-CANCER IN-VIVO IN A NUDE-MOUSE XENOGRAFT MODEL

Objective: To establish the minimum required temperature in cryoablati on of human colorectal cancer cell lines grown as subcutaneous rumors in mice. Methods: Male nu/nu nude mice were inoculated by a sc injecti on of 1 x 10(6) LoVo (n = 30) or C170 (n = 32) cells. After 2 weeks th e tumors were frozen using a 3-mm cryotherapy probe (LCS 3000, Cryotec h, UK) to temperatures ranging from -8 to -84 degrees C. Results: (LoV o) Of 21 mice evaluable for analysis no rumors recurred in 3 mice whic h had their tumors frozen to less than -60 degrees C as measured at th e presumed tumor/host boundary, whereas all but one tumor recurred in 18 mie which had their tumors frozen to >-60 degrees C. (C170) Of 18 m ice evaluable for analysis 14 mice which had their tumors frozen to be tween -8 and -84 degrees C as measured at the presumed tumor/host boun dary developed tumor recurrence. Four mice which had their tumors froz en to -11, -58, -62, and -81 degrees C did not develop tumor recurrenc e. Conclusion: Cryotherapy of subcutaneous human colon cancer xenograf ts in nude mice results in tumor recurrence if tumors are frozen to te mperatures of as low as -60 degrees C (LoVo) or -84 degrees C (C170) w ith a single freeze-thaw cycle. A critical temperature for the effecti ve cryoablation of human colorectal cancer cell lines grown as subcuta neous tumors in mice with a single freeze-thaw cycle was not defined. (C) 1998 Academic Press.