Histologic and biologic response of tumours to irradiation

Abstract

The introduction of radiotherapy was not preceded by any detailed investigation of the biologic effect of the rays on the tumours and the host. At the end of the last century, when the Swedes Sjögren and Stenbeck successfully treated a recurrent cutaneous squamous epithelioma, very little was known about the biology of tumours or the biologic effect of irradiation. The fundamental experimental observations made during the first decade of the twentieth century were concerned mainly with the effect of irradiation of normal cells and tissues such as rabbits testes, plant roots, sea-urchin eggs, fungi, etc. Observations made in different fields were soon correlated, and as early as 1906 Bergonie and Tribondeau were able to formulate their well-known law, which gradually achieved great importance in radiotherapy. The results of treatment were judged with greater caution and more attention was given to the late results. The evaluation of the effects has been supplemented by detailed histologic and cytologic investigations, but knowledge of the cancericidal effect of ionising radiation is still incomplete. This is obvious from modern surveys of the radiobiology of tumours ( Ellinger, 1957; Koller, 1959; Read, 1958; Upton, 1958; Zollinger, 1960). This gap in our knowledge is largely due to the complex biologic nature of tumours, which complicates interpretation of their response to ionising radiation. This complexity is readily recognised in the investigation of tumours from genetic, histopathologic and clinical points of view, but it cannot be observed with certainty in studies of the individual cells.