210 
possibilities of ionizing radiation to 
inhibit the growth of, or to destroy, 
malignant tissue, the use of hormone 
and certain chemical inhibitors, and a 
host of other types of fundamental 
biologic, physical, and clinical research 
are throwing light on the basic prob- 
lem of cancer. 
Two Accepted Forms of Cancer Therapy 
Even with this long background of 
intensive investigation, the only two 
accepted methods of treatment for 
cancer are surgery and radiation 
therapy. With few scattered excep- 
tions, it is only by completely exorcis- 
ing the malignant tumor or by remov- 
ing it in situ with cell-destroying 
radiations that this disease can now be 
controlled or eliminated. Both these 
techniques, often used in combination, 
have resulted in thousands of clinical 
cures, particularly in the case of super- 
ficial malignancies or in deep tumors 
detected in their early stages. Both 
these techniques have improved stead- 
ily with time. The former has pro- 
gressed because of the increasing skill of 
the surgeon and the anesthetist and 
their techniques now permit the re- 
moval of new growths from nearly any 
organ or tissue of the body. The 
latter has depended upon the develop- 
ment of new and more effective forms 
of radiation intelligently employed by 
the radiologist. Cancer of the lip, 
mouth, larynx, uterus, and bladder is 
often treated by radiation alone. 
In addition, radiation plays an indis- 
pensable role in combination with 
surgery for the control of many other 
types of malignant tumors. It is in 
the field of radiation therapy that 
significant contributions have been 
made by the research groups at 
the Massachusetts Institute of Tech- 
nology, where engineering, physical, 
and clinical research on cancer has 
been in progress for more than a 
decade. 
Supervoltage Roentgen-Ray Treatment 
The problem of the radiologist is to 
deliver to the malignant tumor such a 
ANNUAL REPORT SMITHSONIAN INSTITUTION, 1948 
quantity of ionizing radiation as to 
effect its gradual, but complete, 
destruction while causing only a 
tolerable injury to surrounding healthy 
tissue. Particularly in the treatment 
of deep tumors and those concerned 
with vital organs has the use of 
penetrating and ionizing radiation 
been indispensable. Within a few 
months of Roentgen’s discovery the 
therapeutic, as well as the diagnostic, 
value of X-rays had been noted, and 
X-rays were being employed for the 
treatment of superficial lesions. A few 
years later, Madame Curie’s brilliant 
isolation of radium, whose products 
emit a similar but far more penetrating 
radiation, added another powerful 
tool for therapy. During the next 
50 years the relatively low-voltage and 
easily absorbed roentgen rays available 
to Roentgen’s medical confreres have 
been gradually increased to about 
250-kilovolt radiation for the deep- 
therapy application. The limited 
amount of radium is used to an in- 
creasing extent only in direct applica- 
tion to accessible tumors—those on 
the surface or accessible through the 
body orifices. In interstitial therapy 
the gamma-ray emitting needles or 
seeds are inserted into the tumor mass. 
Deep tumors, the most serious clinical 
problem, are now universally irradi- 
ated with roentgen rays in the 250- 
kilovolt energy range, assisted in 
certain cases by gamma-ray irradi- 
ation. 
That higher voltages would produce 
a superior quality of radiation for deep 
therapy has been appreciated for many 
years. During the last decade, how- 
ever, less than a dozen clinical institu- 
tions in the world have had available 
X-ray sources operating in the vicinity 
of 1 million volts. Dr. Robert S. 
Stone of the University Hospital in 
San Francisco has treated patients 
since 1935 with million-volt radiation 
produced by the ingenious high- 
frequency Sloan generator now 
obsolete because of its complexity. 
In 1937 Dr. . Richard) Dresseragou 
Harvard’s Huntington Memorial Hos- 
