184 - A Randomized Controlled Trial of Dose Evaluation in Single-Fraction Electron Beam Radiotherapy for Keloids

10:55am - 11:05am ET

Room 160

Presenter(s)

Deng-Yu Kuo, MD, MPH - Department of Biomedical Engineering, National Yang Ming Chiao Tung University, Taipei, Taiwan

C. C. Lin¹, C. H. Hsieh², P. W. Shueng³, and D. Y. Kuo⁴; ¹Division of Radiation Oncology, Department of Radiology, Far Eastern Memorial Hospital, New Taipei City, Taiwan, ²Division of Radiation Oncology, Department of Radiology, Far Eastern Memorial Hospital, New Taipei City 220, Taiwan, ³School of Medicine, College of Medicine, National Yang Ming Chiao Tung University, Taipei 112, Taiwan, ⁴Department of Biomedical Engineering, National Yang Ming Chiao Tung University, Taipei 112, Taiwan

Purpose/Objective(s):

Postoperative radiotherapy reduces keloid recurrence, yet the optimal single-fraction dose remains undefined. Although 13 Gy provides superior control, concerns regarding long-term toxicity persist. While 9 Gy suppresses fibroblast proliferation in vitro, mechanotransduction in high-tension anatomical sites promotes a pro-fibrotic, apoptosis-resistant phenotype in vivo. We hypothesized that the dose required for effective control is influenced by site-specific biomechanical tension. Therefore, we conducted a randomized trial comparing 13, 11, and 9 Gy to identify a tension-adapted minimal effective dose.

Materials/Methods:

This prospective, randomized, double-blind trial was conducted from February 2020 to December 2023. Patients undergoing keloid excision were randomized to postoperative single-fraction radiotherapy (13, 11, or 9 Gy) within 24 hours using a 6-MeV electron beam. Treatment fields encompassed the surgical scar with a 1.5-cm margin. Bolus thickness was site-specific (5 mm for ears; 3 mm for other sites). Anatomical sites were stratified into high- and low-tension regions per the Ogawa classification. Primary endpoint was 1-year local control; secondary endpoints included objective scar appearance (modified Vancouver Scar Scale, mVSS) and quality of life (QOL) measured by the Skindex score. Outcomes and toxicities (CTCAE v4.03) were assessed through 12 months.

Results:

Of 96 enrolled patients, 88 completed treatment and follow-up. During 1-year follow-up, 14 recurrences occurred (median: 6 months), with rates of 6.9% (13 Gy), 17.2% (11 Gy), and 23.3% (9 Gy). Multivariable analysis identified dose as an independent predictor of recurrence; the 9-Gy group faced a significantly higher risk than the 13-Gy group (OR=5.7, p=0.046), with no significant difference between 11 and 9 Gy. Recurrence occurred in 4.5% of low-tension and 19.7% of high-tension lesions, showing a strong trend toward increased risk in high-tension sites (OR=7.4, p=0.070). Regarding scar appearance, 13 Gy yielded superior mVSS outcomes with a significant dose-by-time interaction (p=0.001) after adjusting for wound width (p=0.017). The 13-Gy group demonstrated sustained QOL improvement. Most patients experienced only Grade 0–1 toxicities; Grade 2 toxicity occurred in 3 patients (3.4%), with no Grade 3+ events.

Conclusion:

Keloid radiotherapy efficacy is dose- and tension-dependent. Multivariable analysis confirms superior recurrence control and aesthetic outcomes with 13 Gy. However, excellent control with 9 Gy in low-tension sites supports a risk-adapted, tension-based dosing strategy to optimize the therapeutic window and minimize unnecessary radiation exposure.