CYCLOPHOSPHAMIDE AS AN ADJUVANT TO X-RAYS IN TREATMENT OF A RADIORESISTANT SOLID TUMOR OF THE RAT, HEPATOMA H-4-II-E

Cyclophosphamide has been given in combination with X-rays in an attempt to improve the therapeutic response of the radioresistant (Do = 3.41 Gy) rat hepatoma H-4-II-E. However, a less than 1 log reduction in surviving fraction of clonogenic cells could be achieved at the maximum tolerated dose of CY. Twenty four hr after a large single dose of the drug, the radiation Do had increased to 3.96 Gy. This observation is discussed in terms of tumor histology and the findings for combined modalities are compared with those for a CY-sensitive rat mammary carcinoma. © 1979.