Experiments with Fractionated X-ray Treatment of the Skin of Pigs. I—Fractionation up to 28 Days

Abstract

Experiments have been carried out to compare the skin reactions in pigs produced by various regimes of fractionated irradiation with X rays, extending up to 28 days. A total of 27 X-ray fields were applied to two pigs. The results show that the major factor which determines the skin response is the size (or number) of the fractions, i.e. the shape of the dose—effect curve. This factor is found to explain approximately five-sixths of the increase of total dose required to produce a given reaction when the dose is divided into five fractions. The remaining one-sixth of the increase is due to tissue repair or repopulation occurring between five and 28 days. The implication in radiotherapy is as follows. If fractionated treatments using fewer and larger fractions are given over the same overall time as a “daily” regime, it is suggested that care must be taken to reduce the total dose below that used in the daily regime, in order to avoid greater skin damage.