Source of Support: None, Conflict of Interest: None
The conventional intra cavitary treatment of cancer cervix with pre loaded or after loaded applicator with Radium, Cs or Cobalt 60 are being replaced by selectron after loading systems. The dose-rate for Brachytherapy is changed from over 0.5.Gy per hour to about 1.7 Gy per hour and because of this change the dose to be delivered by intracavitary insertion is to be reduced by an appropriate percentage. Using clinical data
published so far, a suitable correction factor is arrived at. Even though the correction factors used in various clinical work appear to be varying they fall more or less on smooth curve which gives the correction factor to bring about same normal tissue late reactions. A similar curve has also been obtained to give the same tumour control when selectron is used in the range of 1.5,Gy per hour to 2.0 Gy per hour. Appropriate correction factors are 42 and 47% respectively.