Treatment acceleration in radiotherapy: the relative time factors and dose-response slopes for tumours and normal tissues.
A published collation of data for control of head and neck cancer in over 4500 patients has been subjected to direct analysis to deduce dose-response, fractionation, and time parameters. The analysis confirms the presence of a significant time factor of the order of 0.5-0.6 Gy/day, deduced previously using various assumptions and normalisation procedures. In addition, the dose-response curve was characterised by Da = 29 Gy which contributed to long "effective" doubling times being deduced for tumour clonogens in the patient population as a whole. Some late-reacting normal tissues also show significant time factors, and furthermore, their dose-response curves are in general steeper than for tumours. Hence, care should be taken in accelerating treatments to improve local control, if the treatments are truly at tolerance regarding late-appearing major complications.
Hendry
J H
JH
Cancer Research Campaign Department of Experimental Radiation Oncology, Paterson Institute for Cancer Research, Christie Hospital (NHS) Trust, Manchester, UK.
D004307:Dose-Response Relationship, Radiation; D006258:Head and Neck Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D016013:Likelihood Functions; D011830:Radiation Effects; D011836:Radiation Tolerance; D011879:Radiotherapy Dosage; D013997:Time Factors