LABORATORY STUDIES AND CLINICAL TRIALS OF CHEMICAL RADIO-SENSITIZERS 



The earlier therapeutic experiments with Compound I were sufficiently 

 suggestive to provide a basis for clinical trials, but were far from satisfactory 

 because of the rather small number of animals and the high rate of spon- 

 taneous retrogression of the tumours. This difficulty appears to have been 

 overcome by maintaining the Walker rat carcinoma as ascites tumour and 

 in recent experiments almost invariably using solid tumours at the second 

 passage from the ascites tumour. I wish to thank Professor A. Haddow for his 

 help in supplying animals and tumours, with which to start these experiments. 



Two large-scale therapeutic experiments with tetra-sodium 2-methyl 



1 : 4-naphthohydroquinone diphosphate (Compound I) and tetra-sodium 



2 : 3-dimethyl-l : 4 - naphthohydroquinone diphosphate (Compound 

 XXVIII), on the production of permanent retrogression of the Walker rat 



Figure I. Arrangements for roentgen irradiation of experimental tumour in rat. The rat is wrapped in 

 a flexible lead plate with the tumour projecting through an elliptical aperture. 



carcinoma 256 have now been completed. The details of the experiment 

 with Compound I are summarized in Table I. The results for Compound 

 XXVIII (Mitchell ^ 1953) are compared with those of Compound I in 



Table IL 



Experimental Methods— The main features of this type of animal experiment 

 with the Walker rat carcinoma 256 in the rat, are given in Tables I and //. 

 The following experimental details may be added. 



For the irradiation of the tumours in groups C and D the rat is wrapped 

 up in a lead plate of thickness 1-3 mm with the tumour projecting through 

 an elliptical aperture in the plate of dimensions 4 X 3 -3 cm. A con- 

 venient size for the lead plate is 21 cm X 17 -5 cm transversely ; the elliptical 

 aperture reaches to about 1 cm distance from the middle of the longer edge. 

 The experimental arrangement with the rat held in position in this way for 

 irradiation is shown in Figure 1. The selection of the tumour size in relation 



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