The new vascular disrupting agent combretastatin-A1-disodium-phosphate (OXi4503) enhances tumour response to mild hyperthermia and thermoradiosensitization.

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Hokland SL, Horsman MR

The new vascular disrupting agent combretastatin-A1-disodium-phosphate (OXi4503) enhances tumour response to mild hyperthermia and thermoradiosensitization.

Int J Hyperthermia. 2007 Nov;23(7):599-606.

PubMed ID
18038290 [ View in PubMed
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Abstract

PURPOSE: The aim of this study was to investigate the anti-cancer effect of the novel vascular disrupting agent (VDA), combretastatin-A1-disodium-phosphate (OXi4503), when combined with mild hyperthermia and/or radiation. MATERIALS AND METHODS: A C3H mammary carcinoma was grown subcutaneously in the rear right foot of female CDF1 mice, and treated when a volume of 200 mm(3) was reached. OXi4503 was administered intra-peritoneally at variable doses. Hyperthermia was administered locally to the tumour-bearing foot using a thermostat-controlled water bath. Radiation treatment was performed locally using a conventional X-ray machine. Tumour response was assessed with either a tumour growth time or a tumour control assay. RESULTS: The optimal delay between administration of 50 mg/kg of OXi4503 and hyperthermia was found to be 3 hours. The linear relationship between tumour growth time (TGT) and heating time at a specific temperature resulted in slope values between -0.003 days/min and 0.09 days/min at temperatures between 40 degrees C and 42.5 degrees C. When combined with OXi4503 this was significantly increased to 0.008 days/min and 0.03 days/min at temperatures between 39.5 degrees C and 41 degrees C, respectively. Above 41 degrees C, combined treatment did not result in significantly greater slope values. The radiation dose required to control 50% of the tumours (TCD50) was 52 Gy. Combining radiation with either heat treatment at 41.5 degrees C for 1 hour or OXi4503 reduced the TCD50 to 47 Gy and 41 Gy, respectively. Combining radiation with heat and OXi4503 further reduced the TCD50 to 37 Gy. CONCLUSIONS: OXi4503 is a highly potent VDA, which is capable of significantly enhancing the anti-cancer effect of mild hyperthermia. Mild temperature thermoradiosensitization was also enhanced.

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