The Effects of Timing of Postoperative Radiotherapy on Hypertrophic Scar in a Rabbit Model

BACKGROUND Hypertrophic scar is associated with excessive proliferation of fibroblasts, the accumulation of collagen fibers, and angiogenesis associated with chronic inflammation. Scar resection, combined with radiotherapy, is widely used in clinical practice, but timing remains controversial. This study aimed to investigate the association between the timing of postoperative radiotherapy and the effects on hypertrophic scar in a rabbit model. MATERIAL AND METHODS Forty New Zealand white rabbits, 8-12 months old, weighing 1.8-2.3 kg were used in the model of hypertrophic scar and underwent surgical resection with or without postoperative radiotherapy. The study groups included: Group 1, the non-resection group; Group 2, the resection and non-radiotherapy group; Group 3, the immediate postoperative radiotherapy group; Group 4, the 12-hour postoperative radiotherapy group; Group 5, the 24-hour postoperative radiotherapy group; Group 6, the 48-hour postoperative radiotherapy group; Group 7, the 72-hour postoperative radiotherapy group; and Group 8, the 120-hour postoperative radiotherapy group. The rabbit ear skin was observed after treatment, and the hypertrophic scar index (HI), fibroblast numerical area density (NA), and collagen fiber area density (AA) were determined. RESULTS The HI, NA, and AA were significantly lower after 48 hours of postoperative radiotherapy (P<0.05), with the effects occurring mainly within 24 hours. There was no difference in HI, NA, and AA between the radiotherapy and non-radiotherapy groups within 24 hours after surgery. CONCLUSIONS In a rabbit model of hypertrophic scar, surgical resection combined with radiotherapy resulted in an optimal effect within 24 hours after surgery.