Validity of bioeffect dose response models for normal tissue early and late complications of the skin

SummaryBackgroundThe bioeffect of a physical dose depends on the nature of the tissue, fractionation scheme, dose rate and treatment time. Certainly, experienced radiotherapists are convinced of the existence of patient-to-patient variability in normal tissue response to radiotherapy for malignant tumours. The absorbed dose needs to be translated into a bioeffect dose, which takes into account treatment variables and the radiobiological characteristics of the relevant tissue. Various bioeffect models such as NSD, CRE, TDF and BED have been proposed to predict the biological effect of radiotherapy treatments.AimThis study was aimed at deriving tolerance bioeffect dose values for normal tissue complication rate.Materials/MethodsCompiled clinical data of time dose fractionation schedules and incidence of erythema, desquamation and telangiectasia were used for the present analysis.ResultsFor erythema and desquamation the radiation dose varied from 23.9 to 55.1Gy in 04 to 50 fractions (dose per fraction 1.1 to 7.3Gy) in 11 to 40 days. For telangiectasia (score ≥1 at 3 years) the radiation dose varied from 25.8 to 55.1Gy in 04 to 50 fractions (dose per fraction 1.1 to 7.3Gy) in 11 to 40 days. For telangiectasia (score ≥2 at 5 years) the radiation dose varied from 25.8 to 63.0Gy in 04 to 50 fractions (dose per fraction 1.1 to 7.3Gy) in 11 to 68 days. For telangiectasia (score ≥1, ≥2, ≥3, ≥4 at 10 years) the radiation dose varied from 25.8 to 63.0Gy in 04 to 35 fractions (dose per fraction 1.7 to 7.3Gy) in 22 to 68 days. TDF and LQF values for erythema, desquamation and telangiectasia were evaluated with α/β values of 7.5Gy, 11.2Gy and 2.8Gy respectively. TDF and LQF had a statistically significant correlation with probability of erythema, desquamation and telangiectasia (p<0.001).ConclusionsTDF and LQF values should be limited to 60 and 86Gy in order to limit the probability of telangiectasia.