Dose-response relationship and dose optimization in radiotherapy of postoperative keloids.
OBJECTIVE
The treatment dose and fractionation dose that are considered in postoperative keloids had been reported in the previous studies. We performed retrospective analysis to elucidate the factors influencing the treatment outcome.


METHODS
From 1979 to 1994, 194 lesions in 119 patients received postoperative radiotherapy after excision with the total dose ranging from 16 Gy/8 fr to 40 Gy/8 fr (mean: biologically effective dose (BED) 33.5 Gy). Kilo-voltage X-rays (55 or 100 kVp) or electron beams (4 or 6 MeV), including entire keloid scars, and any suture/puncture holes with a margin around the lesion were used. The median follow-up period was 36 months (range 12-164 months).


RESULTS
Symptomatic pain and itching relief were achieved in 96% and 91%, respectively. The relapse rate was 11% at 20 Gy in five fractions or higher dose, while 43% at less than 20 Gy. On the other hand, the incidence of adverse effects was significantly higher for patients receiving more than 20 Gy in five fractions.


CONCLUSIONS
There was a significant correlation between the relapse rate and the total dose of irradiation, and between adverse effects and the total dose. To correlate local control and adverse effects, we proposed 20 Gy in five fractions as the optimal dose for the postoperative of keloids. A significant correlation between relapse rate and the interval time between excision and radiotherapy was not found in our current study.
Sakamoto
Takashi
T
Department of Radiation Oncology, Kumamoto University, Japan. stakashi@kumamoto-u.ac.jp
Oya
Natsuo
N
Shibuya
Keiko
K
Nagata
Yasushi
Y
Hiraoka
Masahiro
M
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007627:Keloid / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000532:radiotherapy*; D011879:Radiotherapy Dosage