Therapeutic potential of using the vascular disrupting agent OXi4503 to enhance mild temperature thermoradiation.
OBJECTIVE
The response of tissues to radiation with mild temperature hyperthermia is dependent on the interval between the two modalities. This study investigated the effect that the vascular disrupting agent OXi4503 had on this time-interval interaction.


METHODS
The normal right rear foot of female CDF1 mice or foot-implanted C3H mammary carcinomas were locally irradiated (230 kV X-rays) and heated (41.5 °C for 60 min) by foot immersion in a water bath. OXi4503 (50 mg/kg) was injected intraperitoneally 1.5 h before irradiating. Irradiation was performed either in the middle of the heating period (simultaneous treatment) or at 1 or 4 h prior to starting the heating (sequential treatments). Response was the percentage of mice showing local tumour control at 90 days or skin moist desquamation between days 11-23. From the radiation dose response curves the dose producing tumour control (TCD(50)) or moist desquamation (MDD50) in 50% of mice was calculated.


RESULTS
The TCD(50) and MDD50 values for radiation alone were 54 Gy and 29 Gy, respectively. Simultaneously heating the tissues enhanced radiation response, the respective TCD(50) and MDD50 values being significantly (chi-square test, p < 0.05) reduced to 33 Gy and 14 Gy. A smaller enhancement was obtained with a sequential treatment in both tissues. OXi4503 enhanced the radiation response of tumour and skin. Combined with radiation and heat, the only effect was in tumours where OXi4503 prevented the decrease in sensitisation seen with the sequential treatment.


CONCLUSIONS
Combining OXi4503 with a sequential radiation and heat treatment resulted in a 1.4-fold therapeutic gain.
Department of Experimental Clinical Oncology, Aarhus University Hospital , Aarhus , Denmark.
Michael R
MR
Horsman
D000818:Animals; D011756:Diphosphates / Q000378:metabolism / Q000627:therapeutic use*; D005260:Female; D006979:Hyperthermia, Induced / Q000379:methods; D051379:Mice; D008809:Mice, Inbred C3H; D009369:Neoplasms / Q000532:radiotherapy*; D011839:Radiation, Ionizing; D013267:Stilbenes / Q000378:metabolism / Q000627:therapeutic use*
D011756:Diphosphates; C465018:Oxi 4503; D013267:Stilbenes
C3H mammary carcinoma; OXi4503; mild temperature hyperthermia; radiation; vascular disrupting agents