title: The sensitivity of human tissues to changes in dose fractionation: deductions from the RCR survey among UK radiotherapists.
abstract: The dosage prescriptions reported in the Royal College of Radiologists' fractionation survey among radiotherapists have been further analysed using model equations in order to deduce estimates of fractionation-sensitivity parameters for each of the six cases under consideration. For example, using the linear-quadratic model, including a (significant) time factor, with radical treatments of a T2 breast carcinoma or a T1N0 squamous carcinoma of the vocal cord, the (alpha/beta) ratios were 26 +/- 20 Gy and 37 +/- 46 Gy, respectively. The values of the time factor, expressed as the maximum extra dose required per day to counteract the decrease in effect with increasing overall time (gamma/alpha), were 0.60 and 0.45 Gy/day respectively. Using the Ellis formula, which provided a significantly better fit to the dosage prescription (P = 0.003), the exponents of N were calculated to be 0.24 +/- 0.05 and 0.27 +/- 0.07, respectively. The corresponding values of the T exponent were 0.16 +/- 0.06 and 0.014 +/- 0.075. About 20% of radiotherapists prescribed doses greater than +/- 10% from the mean fitted values for the breast treatment, and about 6% of them in the case of the vocal cord.
authors.affiliation: Cancer Research Campaign Department, Paterson Institute for Cancer Research, Christie Hospital and Holt Radium Institute, Manchester, UK.
authors.forename: J H
authors.initials: JH
authors.lastname: Hendry
authors.forename: S A
authors.initials: SA
authors.lastname: Roberts
mesh_terms: D000368:Aged; D001943:Breast Neoplasms / Q000532:radiotherapy / Q000556:secondary; D001984:Bronchial Neoplasms / Q000532:radiotherapy; D002294:Carcinoma, Squamous Cell / Q000532:radiotherapy; D003627:Data Interpretation, Statistical; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000532:radiotherapy*; D011836:Radiation Tolerance; D011879:Radiotherapy Dosage; D012004:Rectal Neoplasms / Q000532:radiotherapy