Radiosensitivity and Tumor Morphology

TO judge of the advantages of treating a patient with radiation is often a more complicated problem than is presented by surgery. In surgery the question is: Can the tumor be completely removed; if it cannot, is any form of palliative operation advisable, and, if so, what? On the other hand, with radiation there are three problems to be solved for each person. One is the amount and quality of the radiation; the others, the situation and sensitivity of the tumor. It is obviously useless to subject patients to large doses of radiation when the tumor is of a type so highly resistant that little can be expected from treatments which must be dangerous in order to be effective. The factor of measurement of quantity is now fairly well settled. Complete tables exist for the percentage penetration of X-rays and gamma rays into the tissues, but the question of dosage as applied to a given morphological picture is still a matter of discussion. A few of the more obvious facts concerning sensitivity have long been known, such as the great difference between basal and squamous cell epitheliomata of the skin, and the impossibility of affecting tumors of the stomach favorably by external radiation. But other fields are still problematical and at the present time considerable effort is being made to correlate the morphology of tumors with their sensitiveness to radiation. Such an understanding is clinically most important, as patients should be spared ineffective or too heavy radiation if lighter doses will be as useful, and it is even more unjust perhaps to treat too lightly tumors which will yield only to maximum doses. Radiation sensitivity, as generally used, has hitherto often suggested two points of view, at times somewhat confused. One is mathematical and implies some precise method which will record this biological quality of the cells; the other is clinical and is estimated only by the temporary disappearance of tumor masses and ultimately by the duration of life of the treated patient. For this reason a vast amount of inaccuracy has crept into nearly all discussions and it is most important to remember in which sense the words are used. It is the object of this paper to review our knowledge of the subject and to collect such correlations as exist between the morphology of cells and the probability of destructive influences being exerted upon them by radiation, rather than to predict the survival or death of the patients who may possess such tumors. Optimism has led some to assume that a radio-sensitive tumor implies a cured patient, but this is very frequently a wholly impossible conclusion. Certain tumors, locally removable by surgery but rapidly fatal with or without operation, have an unfortunate tendency to behave in the same fashion when treated by radiation.