Characterization of mild whole-body hyperthermia protocols using human breast, ovarian, and colon tumors grown in severe combined immunodeficient mice.

OBJECTIVE: We have shown that one treatment of fever-like whole body hyperthermia (WBH) on mice bearing human breast tumors results in a tumor growth delay. Our goal was to repeat this study in mice bearing human ovarian or colon tumors. We further evaluated this WBH protocol by performing multiple and interrupted WBH treatments.
METHODS: Human tumors were grown in severe combined immunodeficient (SCID) mice. For WBH, core body temperatures were maintained at 39.8+/-0.2 degrees C for 6-8 hours. Multiple treatments were given 6-7 days apart. Interrupted WBH consisted of three 2-hour heatings, 15 minutes apart. Tumor growth time (TGT) was the number of days to grow 1.5 or 2 times in volume.
RESULTS: For WBH-treated ovarian tumors, TGT was 12+/-1.2d, compared with 5.0+/-0.1d for untreated mice (P < 0.05). For colon tumors with one WBH treatment TGT was 4.4+/-1.1d. Two and three treatments had TGTs of 9+/-2.3d and 8+/-1.6d. For the untreated tumors, TGT was 2+/-0.7d (P < 0.01 for one, two, and three treatments). Histological examination indicated that one and two treatments were associated with cellular damage within the tumors. With a slower growing colon tumor, the TGT was 24+/-3.3d with three WBH treatments, compared with 14+/-1.8d for controls (P < 0.01). The TGT of breast tumors treated with interrupted WBH was not significantly different than the noninterrupted, with TGT of 7.3+/-0.8d and 6.2+/-1.0d, respectively.
CONCLUSIONS: These data illustrate that WBH causes a tumor growth delay in mice bearing human ovarian and colon tumors. This response is enhanced with a second treatment of WBH. Interrupted and noninterrupted WBH give comparable anti-tumor results. We will continue to evaluate WBH in various animal models to optimize its potential for clinical administration and maximize the anti-tumor response.