148 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 194 5 



water (pi. 4, fig. 2). A small hole was left through which a canalized 

 beam of neutrons emerged. The attempts began in 1938, and caution 

 was needed because of the danger of serious damage to normal tissue. 

 Cancer patients were chosen, however, whose condition was hopeless 

 from every other point of view. This was perhaps hardly a fair test 

 of the usefulness of a neutron beam in medicine, and it was not to be 

 expected that the results would be in any way spectacular. To begin 

 with, 24 patients, all in the advanced stages of their disease, repre- 

 senting hopelessly incurable cancer, received cautiously administered 

 doses, the magnitude of which was determined in a purely arbitrary 

 fashion (10). Because of the fixed limitations of space, at first only 

 lesions confined to the head and neck could be treated. These experi- 

 ments served to supply information concerning skin tolerance, depth 

 dosage, and the nature of the primary response of tumor tissue. 

 Later on, with an improved lay-out, a larger number of patients were 

 given neutron irradiation, and these provided a wide diversity of 

 tumors including sites other than the head and neck. So far the 

 results have not been too good (table 3). But neutrons have already 

 caused the disappearance of a malignant growth (23), though no such 

 case is regarded as a cure until several j^ears have elapsed since treat- 

 ment. Compared with the results of X- and gamma radiation of 

 cancer, neutrons have not so far proved better, but they have been 

 useful in a few instances where X-rays had been tried and failed. It 

 will obviously take time to discover what is the best way in which to 

 give them, e. g., what should be the total dose, intensity, number of 

 exposures, over-all time, the precise method of combination with other 

 types of radiation, and so on. 



Table 3. — Some effects of neutrons on cancer 



[See rcf. 2361 



Number of patients 



Effect 



Complete regression. 



Partial regression 



No regression 



Recurrence in treated area 



Dead 



Incomplete information... 



A great deal of experimental work has been going on besides the 

 relatively few therapeutic trials which have been made, and the 

 biological effects of neutrons on a variety of tissues have been studied 

 and the results compared with those produced by other types of pene- 



