Effects of hyperthermia on a neurogenic rat cell line (BT4C) in culture. Development of thermal tolerance during continuous heating

Clinically derived dose effect relationship for hyperthermia given in combination with low dose radiotherapy

A group of 36 patients, treated on 44 fields with fractionated treatments of local high-frequency induced hyperthermia and radiotherapy to the low total dose of 14-25 Gy, was retrospectively evaluated for differences between responders (i.e., complete and partial responders) and non-responders. A response rate of 86% was achieved, comprising 14% (6/44) complete and 73% (32/44) partial response. There was an indication that the probability of complete response is greater in smaller tumours. The tumour temperatures achieved were higher in the responders than in the non-responders. Logistic analysis was performed on the mean temperature achieved. This temperature parameter yielded a significant positive dose-effect relationship with regard to therapeutic effect, from which a 50% effective dose of 38.8 degrees C was calculated. The data indicate that to obtain the maximum therapeutic effect, i.e., greater than 95% response rate, tumour temperatures above 42.5 degrees C need to be achieved.

[Effect of local moderate hyperthermia in combination with N-nitroso-1,3-bis-(2-chloroethyl)urea (BCNU) and 5-fluoro-(tetrahydro-2-furyl)uracil (ftorafur) on induced autochthonous colonic cancers in the rat. 3: Polychemotherapy in combination with hyperthermia]

The use of hyperthermia for the treatment of tumors has been tested in vitro and in vivo experiments as well as clinically for a long time. Combination of hyperthermia with chemotherapy was reported to result in overadditive cytostatic effects. In a clinically adapted, controlled animal experiment, local moderate hyperthermia (43.5 degrees C, 3 X 60 min) alone and in combination with polychemotherapy (BCNU) and Ftorafur) was used for the treatment of AMMN-(N-nitrosoacetoxymethyl-methylamine) induced autochthonous colonic carcinomas in Sprague-Dawley rats. Diagnosis and follow-up inspections were carried out endoscopically. The applied therapies did not result in prolonged survival times, nor was an additive effect seen after combined hyperthermia and chemotherapy in this "hard", i.e. relatively chemotherapy-resistent, tumor model.

Hyperthermic potentiation of doxorubicin and 4'-epi-doxorubicin in a transplantable neurogenic rat tumor (BT4A) in BD IX rats

The combined effect of hyperthermia and doxorubicin on the neurogenic rat cell line BT4C was found to be synergistic in vitro. The present investigation was initiated to study if this synergistic effect also could be obtained in vivo. An enhanced effect occurred when doxorubicin and 4'-epi-doxorubicin 7 mg/kg body weight were given 30 minutes prior to local water bath hyperthermia (one hour at 44.0 degrees C). The local side effects of the combined treatment did not increase above that of hyperthermia alone. Therefore, local hyperthermia may become a useful modality for enhancement of the effect of anthracyclines on tumors with marginal drug sensitivity or bulky tumors with poor drug penetration.

Sensitization of clonogenic malignant cells to hyperthermia by glucose-mediated, tumor-selective pH reduction

The fraction of clonogenic cells (as assayed by colony formation in semisolid agar medium) in neurogenic TV1A tumor transplants carried subcutaneously by hyperglycemic BDIX rats (serum glucose concentration 50 mmoles/1; average intratumoral pH 6.1) was reduced by a factor of approximately 2.5 X 10(3) after in vivo exposure to 42.2 degrees C for 1 h. The corresponding reduction factor for TV1A tumors in normoglycemic rats was about 20 (serum glucose concentration 6 mmoles/1; average intratumoral pH 6.9). Hyperglycemia without hyperthermic treatment reduced clonogenicity by a factor of about 18 ("glucose-mediated suicide").

Effect of hyperthermia on a neurogenic rat cell line (BT4A) in vivo

The effect of hyperthermia alone on the growth of the BT4A neurogenic tumour implanted into the feet of BD IX rats has been investigated. Following treatment by immersion of the tumour-bearing leg in a water bath at 42.0 to 45.0 degrees C a temporary retardation of tumour growth was observed but no cure. The lag phase before regrowth occurred was temperature and time dependent. A log-liner correlation was found between the surviving fraction previously found in vitro and the heat sensitivity of the cell line in vivo.