Since the late 1980s, there has been a strong focus on the importance of overall treatment time for the outcome of curative radiotherapy in head and neck carcinomas. Experience from split-course irradiation had repeatedly indicated that such treatment yielded inferior results, and the overview by Withers et al. (2) made it clear that accelerated repopulation was a prominent clinical feature. Based on these observations, a number of large-scale randomised clinical trials was introduced in the early 1990s, most of them comparing conventional radiotherapy with various schedules of accelerated fractionation ranging from simply increasing the number of weekly fractions from five to six [DAHANCA 7, (4, 5)] or seven [CAIR (6)]. Also more elaborate schedules with hyperfractionated accelerated split-course [EORTC (7)] or concomitant boost [RTOG (3, 8)] have been implied, and the most radical was the CHART study, where a very rapid treatment schedule was introduced with 54 Gy in 36 fractions in 12 consecutive days. In contrast to the other trials where there was no major reduction in total dose, the CHART trial traded in total dose for a reduction in overall treatment time under the assumption that less dose would be necessary providing a treatment was given in a few weeks. The result of the randomised trials, which have included several thousand patients, almost uniformly indicated the benefit of accelerated fractionation was improved tumour control. Unfortunately, most treatment schedules were associated with an increased acute morbidity, and in some trials this also resulted in a consequential excess late morbidity which became dose limiting. The studies therefore also demonstrated limitations in accelerated fractionation, and it appears that a dose intensity which, on average, goes beyond 12 Gy per week in 2-Gy fractions may be too intensive, depending on the volume included. Thus the most simple schedule which has emerged from the trials has been the DAHANCA 7 schedule with six fractions of 2 Gy per day and the similar concomitant boost treatment (RTOG) in which the extra doses are given at the end of the treatment but with the same overall treatment time. Although such an accelerated schedule reduced the total treatment time by only approximately 1 week, it resulted in a significant improvement in local control without unacceptable excess late morbidity. As mentioned before, the CHART schedule differed in its design by giving a considerably smaller total dose in a very short overall treatment time. The outcome of the study, in comparison with conventional fractionation, was that there was no difference in tumour control but a reduced late morbidity. This was expected since the two schedules were designed to have equal strength, and the CHART schedule therefore gave the important message that the total dose could be traded with time.
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