[Accelerated fractionation]

Abstract

Accelerated repopulation is a reason for loco-regional failure after radiotherapy for head and neck carcinoma. Accelerated fractionation(AF) is a radiotherapy regimen reducing the total treatment time, with the aim of counteracting tumor cell repopulation. AF administers the same or a similar total dose as conventional treatment in a reduced overall time by giving conventionally-sized or smaller fractions more than once daily. Several different clinical trials on AF have proved to be of benefit in loco-regional control, although no benefit in survival was generally detected. The metaanalysis of altered fractionated radiotherapy in head and neck cancer has showed a benefit with AF with conventional fractionation(CF). However, the magnitude of the survival benefit is lower with AF than with hyperfractionation (HF). In particular, AF using reduced total doses or a split course does not improve treatment benefits. AF that employs continuous RT schedules, without compromising the total dose, improves local control. More data on this AF regimen are needed. Acute morbidity is significantly more frequent with AF. Whether late toxicity is also worse with AF is unclear. Some trials suggest no increase in late toxicity, while others suggest the opposite. The effect of AF seems to be greater for the primary tumor than for the metastatic lymph-nodes. Also, the reduction of the treatment time is more beneficial in well- to moderately-differentiated tumors.