Abstract
The biological effects of different fractionation schemes were evaluated by the histological examination of bronchial carcinomas removed at operation or autopsy following radiotherapy. Radiation was given in daily, small fractions (200 cGy [centrigray or rad], large fractions (600 cGY) every 5th day or a single high dose followed by daily low-dose treatment. The highest proportion of tumors free of viable cells was found in patients receiving small daily fractions in operable and inoperable tumors. This apparent change in radio-sensitivity with different fractionation schemes is discussed.