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Abstract

Purpose:

The tumor growth kinetics of the human LoVo colorectal xenograft model was assessed in response to vandetanib, an orally available receptor tyrosine kinase inhibitor, radiotherapy (RT), or irinotecan (CPT-11), as single therapies and in combination.

Methods and Materials:

LoVo cells were injected subcutaneously into the right hind limb (5x106 cells in 100μL phosphate-buffered saline) of athymic NCR NUM mice and tumors were grown to a volume of 200–300mm3 before treatment. Vandetanib was administered at 50 mg/kg daily orally for 14 days starting on Day 1. RT was given as three fractions (3x3 Gy) on Days 1, 2, and 3. CPT-11 was given at 15 mg/kg intraperitoneally on Days 1 and 3. Tumor volumes were measured on a daily basis and calculated by measuring tumor diameters with digital calipers in two orthogonal dimensions.

Results:

All three single treatments (vandetanib, CPT-11, and radiation) significantly slowed LoVo colorectal tumor growth. Vandetanib significantly increased the antitumor effects of CPT-11 and radiation when given in combination with either of these treatments. These treatment combinations resulted in a slow tumor growth rate during the 2 weeks of vandetanib administration. The triple combination of vandetanib, CPT-11, and radiation produced the most marked improvement in response as observed by measurable shrinkage of tumors during the first week of treatment.

Conclusions:

The tumor growth delay kinetics observed in this study of the LoVo colorectal model suggest concurrent and sustained post-sequencing of vandetanib with cytotoxic therapy may be beneficial in tumors of this type.

Reprinted from International Journal of Radiation Oncology*Biology*Physics, Volume 75, Edition 3, Wachsberger P, Burd R, Ryan A, Daskalakis C, Dicker AP: “Combination of Vandetanib, Radiotherapy, and Irinotecan in the LoVo Human Colorectal Cancer Xenograft Model”, pages 843-853, November 1, 2009.

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