Biologically effective doses of postoperative radiotherapy in the prevention of keloids - Dose-effect relationship

Purpose: To review the recurrence rates of keloids after surgical excision followed by radiotherapy, and to answer the question whether after normalization of the dose, a dose-effect relationship could be derived. Material and Methods: A Literature search was performed to identify studies dealing with the efficacy of various irradiation regimens for the prevention of keloids after surgery. Biologically effective doses (BEDs) of the various irradiation regimens were calculated using the Linear-quadratic concept. A distinction between recurrence rates of keloids in the face and neck region and those in other parts of the body was made. Results: 31 reports were identified with PubMed with the search terms keloids, surgery, radiation therapy, radiotherapy. 13 reports were excluded, because no Link could be found between recurrence rate and dose, or if Less than ten patients per dose group. The recurrence rate for surgery only was 50-80%. For BED values > 10 Gy the recurrence rate decreased as a function of BED. For BED values > 30 Gy the recurrence rate was < 10%. For a given dose, the recurrence rates of keloids in the sites with high stretch tension were not significantly higher than in sites without stretch tension. Conclusion: The results of this study indicate that for effectively treating keloids postoperatively, a relatively high dose must be applied in a short overall treatment time. The optimal treatment probably is an irradiation scheme resulting in a BED value of at Least 30 Gy. A BED value of 30 Gy can be obtained with, for instance, a single acute dose of 13 Gy, two fractions of 8 Gy or three fractions of 6 Gy, or a single dose of 27 Gy at Low dose rate. The radiation treatment should be administered within 2 days after surgery.