ROENTGEN RAYS AGAINST CANCER—TRUMP 
choice of treatment distance, field size, 
number of portals through which the 
radiation is directed, and fractiona- 
tion technique by which he distributes 
the total dose over a period of days or 
weeks. More often than not, how- 
ever, in the present treatment of deep- 
seated malignancies, the tumor dose 
is established not by the optimum 
amount required to destroy the tumor, 
but rather by the tolerance of the 
surrounding normal tissue and skin 
through which the radiation must 
pass. Most deep tumors treated with 
200-kilovolt radiation can be reduced, 
if at all, only by doses which produce 
a violent skin reaction and the ab- 
sorption of sufficient ionizing energy 
by the patient to produce nausea and 
other physiological disturbances. In 
the clinical program at M. I. T. it 
was found that both of these difficul- 
ties have almost entirely disappeared. 
Doses have been delivered to the site 
of a deep tumor sufficient to cause its 
regression with only mild skin ery- 
thema or no skin reaction at all. 
Patients have been treated for ab- 
dominal tumors with little or no 
systemic reaction. Clearly the possi- 
bility has been developed for the first 
time of delivering to a deep tumor a 
dose defined primarily by the require- 
ments at the tumor site rather than 
the tolerance of intervening tissue. 
A second advantageous property for 
deep therapy of supervoltage roentgen 
rays is the substantial increase in 
penetration of the radiation beam. 
For a given dose sustained in the 
region of the skin, 3-million-volt rays 
will deliver twice as much ionization 
energy to a tumor at a depth of 10 
centimeters as will 200-kilovolt rays. 
As a result, deep tumors can be much 
more efficiently irradiated with less 
damage to surrounding healthy struc- 
tures and less total ionizing energy 
absorbed within the body of the 
patient. 
Radiologists have often employed 
the “cross-firing”’ technique as a means 
of delivering a high tumor dose with 
a minimum of external skin damage. 
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In such procedure the tumor is irradi- 
ated from several directions so that 
the dose is cumulative in the tumor, 
but distributed in the surrounding 
healthy tissue and skin. When this 
technique is likewise applied with 
supervoltages, unusual selectivity of 
radiation dose is accomplished. Cross- 
firing from three directions results in 
a deep tumor dose which is greater 
than the highest dose sustained else- 
where in the tissue. Using a continu- 
ous cross-firing technique with super- 
voltage rays, it becomes possible to 
deliver to a localized deep tumor 
dosages which are six times higher 
than those absorbed by even nearby 
healthy tissue. Thus the dream of the 
radiologist of delivering to arbitrarily 
selected regions deep within the body 
cell-destroying ionization far greater 
than that sustained in other regions 
becomes attainable. 
Unfortunately the clinical problem 
is often more complicated. Deep- 
seated malignancies may not be well 
defined. Tumors of the bladder, uter- 
us, larynx, and thorax are often 
localized, whereas other common can- 
cer types are likely to have nearby or 
distant extensions from the primary 
tumor site. Metastasis from the pri- 
mary tumor along the lymph nodes is 
a common characteristic which re- 
quires that these distributed regions of 
possible malignancy must be found 
and destroyed. The probable areas 
where metastasis might occur are often 
fairly definitely known from clinical 
experience so that preventive radia- 
tion therapy may be initiated even 
before symptoms appear. It is per- 
haps even more important to treat 
effectively the periphery of malignant 
regions and their actual or anticipated 
metastases than to concentrate on the 
primary tumor. Although this clinical 
problem is more complicated, the use 
of more penetrating, less scattering, 
and more skin-favoring supervoltage 
radiation, combined with real diag- 
nostic and radiologic skill, should pay 
dividends in increased comfort and 
life of the patient. 
