Linear-quadratic model isoeffect relations for proliferating tumor cells for treatment with multiple fractions per day.
A modified linear-quadratic model isoeffect relation that includes the effect of proliferation is proposed. As for a planned course of therapy, the treatment time T and the number of fractions N are not independent variables; the new isoeffect relation involves only the fraction size d and the total dose D, but differs from the unmodified linear-quadratic model isoeffect relation and predicts higher isoeffect doses for small dose fractions. Using the new isoeffect relation it is explicitly shown, for a simple model, that decreasing the fraction size will improve the therapeutic ratio only if multiple fractions per day are given.
Department of Radiation Medicine, University of Kentucky Medical Center, Lexington 40536-0084.
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Yaes
D002455:Cell Division / Q000528:radiation effects*; D006801:Humans; D008433:Mathematics; D011879:Radiotherapy Dosage; D013116:Spinal Cord / Q000528:radiation effects*; D013120:Spinal Cord Neoplasms / Q000532:radiotherapy*