The sensitivity of human tissues to changes in dose fractionation: deductions from the RCR survey among UK radiotherapists.
AffiliationCancer Research Campaign Department, Paterson Institute for Cancer Research, Christie Hospital and Holt Radium Institute, Manchester, UK.
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AbstractThe 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.
CitationThe sensitivity of human tissues to changes in dose fractionation: deductions from the RCR survey among UK radiotherapists. 1991, 3 (1):22-7 Clin Oncol (R Coll Radiol)
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