In vivo destruction of tumor tissue by cryoablation can induce inhibition of secondary tumor growth: An experimental study

Background. Cryoablation has been used successfully for the local treatment of several cancers. Besides local destruction, a systemic antitumor respon se has been postulated after cryoablation of rumor tissue. In this study we evaluate the possible systemic antitumor response induced by cryodestructi on of tumor tissue in two mouse tumor models. Methods. Mice received two su bcutaneously placed tumor implants (thigh and flank) of the non-immunogenic mouse colon tumor cell line, colon 26-B. After 7 days. the thigh implant w as treated by cryoablation or excision and the effect on secondary tumor gr owth was determined by volume measurement of the nontreated Rank tumor. Cyt okine (IL-1 alpha and TNF-alpha) levels in plasma were measured after treat ment. Similar experiments were performed in nude mice using a human melanom a cell line (MV3). Moreover. in this model the effect of cryoablation on de velopment of spontaneous lung metastases was evaluated. Results. In the col on 26-B tumor model treatment of primary tumor implants by cryoablation res ulted in a significant inhibition of secondary tumor growth compared to ani mals treated by surgical excision (P < 0.01). Six hours after treatment. pl asma levels of IL-1 alpha and TNF-alpha were higher after cryoablation than after excision (P < 0.01). Also in the nude mice model cryoablation result ed in inhibition of secondary tumor growth, though not significant. Mice tr eated by cryoablation showed significantly less lung metastases compared to those treated by excision (P = 0.03). Conclusions. Cryoablation of tumor t issue can result in inhibition of secondary and metastatic tumor growth. A cytokine response induced by cryoablation of tumor tissue mag attribute to this feature. (C) 2001 Academic Press.