[Practical use of the TDF factor in radiotherapy of basalioma and squamous cell carcinoma]

For X-ray therapy, the relation between single doses, number of fractions and duration of therapy have been combined in the TDF (time, dose, fraction) factor by Orton and Ellis. This factor seems to be well suited to evaluation of the X-ray therapy of basal cell carcinomas and squamous cell carcinomas of the skin. A simplified TDF formula is presented, together with some methods of calculation. Furthermore, tables are presented containing TDF values for frequently applied single doses and for two to five fractions per week. In addition, some hints are given on the use of the decay factor of Orton and Ellis to compensate for the loss of X-ray effectiveness if therapy has been interrupted.