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RESEARCH PRODUCT

Cryoablation of Human Colorectal Cancerin Vivoin a Nude Mouse Xenograft Model

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Abstract Objective: To establish the minimum required temperature in cryoablation of human colorectal cancer cell lines grown as subcutaneous tumors in mice. Methods: Male nu/nu nude mice were inoculated by a sc injection of 1 × 10 6 LoVo ( n = 30) or C170 ( n = 32) cells. After 2 weeks the tumors were frozen using a 3-mm cryotherapy probe (LCS 3000, Cryotech, UK) to temperatures ranging from −8 to −84°C. Results: (LoVo) Of 21 mice evaluable for analysis no tumors recurred in 3 mice which had their tumors frozen to less than −60°C as measured at the presumed tumor/host boundary, whereas all but one tumor recurred in 18 mice which had their tumors frozen to >−60°C. (C170) Of 18 mice evaluable for analysis 14 mice which had their tumors frozen to between −8 and −84°C as measured at the presumed tumor/host boundary developed tumor recurrence. Four mice which had their tumors frozen to −11, −58, −62, and −81°C did not develop tumor recurrence. Conclusion: Cryotherapy of subcutaneous human colon cancer xenografts in nude mice results in tumor recurrence if tumors are frozen to temperatures of as low as −60°C (LoVo) or −84°C (C170) with a single freeze–thaw cycle. A critical temperature for the effective cryoablation of human colorectal cancer cell lines grown as subcutaneous tumors in mice with a single freeze–thaw cycle was not defined.