Optimizing the time course of brachytherapy and other accelerated radiotherapeutic protocols

Dynamic optimization of a linear–quadratic model with incomplete repair and volume-dependent sensitivity and repopulation

“…More recently, the temporal -or dynamic -optimization of a LQ model with different repair rates for early and late tissues has generated a further therapeutic advantage by incorporating acute fractions at the beginning and end of treatment [21].…”

“…The first gap is that the elegant analysis in [21] appears to be the only study that systematically investigates the dynamic optimization of the LQ model. It focuses on accelerated regimens (e.g., brachytherapy), and the use of temporal optimization to exploit the irregular time intervals present in traditional non-accelerated protocols has yet to be studied.…”

Pulse Frequency in Pulsed Brachytherapy Based on Tissue Repair Kinetics

“…The great influence of tissue-repair kinetics on the biological effect in four different pulse schemes was also discussed in their paper. A treatment regimen with two pulses of higher dose, one at the beginning and one at the end of the pulse scheme, might be another option to improve the therapeutic gain (19). A regimen with different pulse doses cannot yet be defined as a single treatment in presently available commercial planning software.…”

How to Optimize Therapeutic Ratio in Brachytherapy of Head and Neck Squamous Cell Carcinoma?

“…However, the main question is whether or not the increased effect is greater on late-responding normal tissues than on tumour cell kill. To reproduce the biological effects of LDR brachytherapy using a PDR remote afterloading system, Brenner & Hall (43,44) and Fowler & Mount (45) recommended the same total dose, the same dose rate (typically, about 0.5 Gy/h), pulse length 10 min or more (or dose rate not exceeding 3 Gy/h during pulse) and, pulse repeated each hour (typically, 0.5 Gy). If these conditions are met, the biological effects of PDR radiation therapy should be equivalent to those of LDR radiation therapy, for all tissues.…”

“…In 1994, Brenner & Hall exploited this difference to design new radiotherapeutic regimens (44). Using a T 1/2 of 0.5 h for early-responding tissues and of 4 h for late-responding tissues, they estimated that PDR brachytherapy delivering a series of pulses at intervals of 3 -4 h should produce better results than LDR brachytherapy.…”