Comparison of conventional and split-course radiotherapy as primary treatment in carcinoma of the larynx.
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.
Overgaard
J
J
Department of Experimental Clinical Oncology, Danish Cancer Society, Aarhus C.
Hjelm-Hansen
M
M
Johansen
L V
LV
Andersen
A P
AP
D002294:Carcinoma, Squamous Cell / Q000532:radiotherapy*; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D007822:Laryngeal Neoplasms / Q000532:radiotherapy*; D011878:Radiotherapy / Q000379:methods*; D011879:Radiotherapy Dosage