Comparison of Conventional and Split-Course Radiotherapy as Primary Treatment in Carcinoma of the Larynx

Abstract

Based on our experience with conventional, daily irradiation, a split-course radiation schedule was introduced in 1978. The schedule, which was based on Cohen's models for squamous cell carcinoma and vascular damage respectively, predicted an improved tumour control and a reduced rate of late complications, e.g. late oedema, if the conventional, daily treatment was replaced by a split-course schedule. The schedule has later been abandoned, but the experience gained from split-course treatment at various dose levels has been analysed and the results compared with those obtained by conventional radiation. The data allowed construction of dose-response curves and estimation of iso-effect doses. Split-course treatment was associated with a significantly reduced therapeutic ratio because, disappointingly, it did not improve tumour control, and the severity of late complications grew. No late complications were avoided by introducing a 3-week pause in the radiation therapy regimen, nor was the tumour response improved despite a 12-Gy increase in total dose. This indicates a significant repopulation corresponding to more than 0.5 Gy/day, equivalent to an up to 100-fold increase of the number of clonogenic tumour cells during the pause--an increase that occurred despite the decrease, clinically, of the tumours during this period.

Advanced Squamous Cell Carcinoma of the Larynx

“…An interim report from this trial has shown a better total survival compared to the earlier trial with split-course therapy, probably related to the change in treatment schedule (6). However, this trial is still on-going and no definite results can yet be reported.…”

Radical Surgery and Postoperative Split-Course Radiotherapy in Squamous Cell Carcinoma of the Head and Neck—Factors Influencing Local Control and Survival

“…However, when the break, is compensated by a lo'%, increase in total dose, split-course seems to be equally effective as continuous treatment (25). Overgaard et al (26) used a 20'% increase in the total dose but this caused a significant increase of late complications. In the present analysis, using both univariate and multivariate approaches, neither overall treatment time of radiotherapy nor duration of the split pause appeared as prognostic factors for local control or survival.…”

Primary Radiotherapy of Tl and T2 Glottic Carcinoma: Analysis of treatment results and prognostic factors in 223 patients

“…In the univariate analysis a treatment interruption of 7 days or more showed a significant impact, but this was lost in the multivariate analysis. Several authors have shown total treatment time to predict treatment outcome and therefore treatment interruptions are not recommended (16,18,22,24,25,27).…”