Response of intramuscular Walker 256 rat tumor to sustained-release cyclophosphamide and ARA-C capsules

Randomly bred Sprague-Dawley rats with the intramuscular form of Walker 256 tumor growing in the right thigh region were treated with sustained-release cyclophosphamide capsules as well as with cytosine arabinoside capsules. A disk-shaped caps-le was implanted subcutaneously adjacent to the tumor mass. Tumor regression, weight gain, and prolongation of lifespan were observed in animals treated with cyclophosphamide capsules of 10 mg or 20 mg total drug content each. However, the walker 256 intramuscular tumor did not respond to ARA-C capsules implanted, and the animals died at the same rate as the controls, with large ulcerated tumor masses and some metastasis. The in vitro diffusion data of ARA-C capsules is shown. Gross and histological changes associated with cyclophosphamide administered in this manner are reported.