International journal of radiation oncology, biology, physics 2011-03-15
A radiobiological analysis of multicenter data for postoperative keloid radiotherapy.
Abstract
Purpose
To identify factors significantly affecting recurrence rates after postoperative external beam radiotherapy (XRT) of keloids, and to delineate any radiation dose response and effects of radiation dose per fraction.
Methods and materials
A comprehensive literature review was performed to compile a database of 2,515 resected keloids (36.9% earlobe). Postoperative XRT was 45- to 100-kV X-rays in 27.0% or 120- to 250-kV X-rays in 11.1%, Co-60 in 1.9%, Sr-90 in 4.7%, 1.5- to 9-MeV electrons in 26.5%, and no XRT in 28.8%. In the 1,791 irradiated patients, the median radiation parameters were as follows: total dose, 15 Gy (range, 6-30 Gy); dose per fraction, 5.0 Gy (range, 2-15 Gy); fractions, 3 (range, 1-10); and time, 7 days (range, 0-33 days).
Results
Multivariate stepwise logistic regression correlated decreased keloid recurrence with earlobe location (p = 1.98E-10; odds ratio, 0.34), biologically effective dose (p = 1.01E-27), and treatment with electron beam or Co-60 vs. other techniques (p = 0.0014; odds ratio, 0.72). Different radiobiological models calculated values of α/β = 1.12 to 2.86 (mean, 2.08) and time (repopulation) correction factors for biologically effective dose from 0.98 to 2.13 Gy per day (mean, 1.34) starting 10 days after surgery. Different models (with α/β = 2.08) predicted that doses needed for 90% and 95% control with 3 fractions of postoperative electron beam were 16.0 to 16.2 Gy and 18.3 to 19.2 Gy, respectively, in less than 10 days for earlobe keloids and 21.5 to 22.2 Gy and 23.4 to 24.8 Gy, respectively, in less than 10 days for other sites.
Conclusions
Postoperative keloid radiotherapy requires moderately high doses and optimal technique to be effective. The relatively low α/β ratio indicates that radiotherapy with a limited number of fractions and high doses per fraction is the best strategy.
Related Questions
Can patients receive adjuvant radiation therapy after keloid excision without primary closure, or would radiation impede healing by secondary intention?
I have personally treated several patients where primary closure was not obtained due to the large size of the keloid (back and anterior mid-chest). Due to the limitation of raising a large flap around these regions to close the wound primarily and poor take rates of a skin flap, these resections we...
Is there a role for re-irradiation of a recurrent keloid?
The answer is yes.We follow the dose schedule as highlighted in this review by Dr. Flickinger.Flickinger, PMID 20472370.
What is your regimen for treating a keloid with radiation alone?
Our institutional experience (Hoang, Aesthet Surg J 2017) has largely been with post-excisional RT, although at our institution we have on occasion treated definitively with RT alone. We do not have a standardized regimen for primary RT at our institution and the Malaker et al article is the only pu...