Background
Systematic review and BED meta-analysis. 84 studies (retrospective and prospective), 4,485 keloid lesions treated with postoperative RT. Evaluated the relationship between biologically effective dose (BED) and keloid recurrence rate. Aimed to determine the optimal RT dose/fractionation for keloid prevention after surgical excision. Kal HB et al, IJROBP 2009.
Interventions and follow up
Arm A: Various postoperative RT regimens: single fraction (5–10 Gy) to hypofractionated (15–20 Gy/3–4 fractions) to conventional fractionation (30–40 Gy/15–20 fractions)
Primary endpoint: Keloid recurrence rate vs BED
mFollow up: 1–5 years across studie
Primary endpoint: Keloid recurrence rate vs BED
mFollow up: 1–5 years across studie
Results
Comparison: BED calculations (α/β = 10 Gy assumed for keloid fibroblasts) vs recurrence rate
Recurrence rate (BED <30 Gy): ~45%
Recurrence rate (BED 30–40 Gy): ~20%
Recurrence rate (BED >40 Gy): ~14% — plateau of dose-response
Optimal BED: ~30–40 Gy equivalent; single fraction ≥10 Gy or 15 Gy/3 fractions achieve BED ~30–40 Gy
Recurrence rate (BED <30 Gy): ~45%
Recurrence rate (BED 30–40 Gy): ~20%
Recurrence rate (BED >40 Gy): ~14% — plateau of dose-response
Optimal BED: ~30–40 Gy equivalent; single fraction ≥10 Gy or 15 Gy/3 fractions achieve BED ~30–40 Gy
Adverse events
Main adverse events: RT near critical structures (ear, eyelid, sternal skin): secondary malignancy risk is theoretical at low doses (<20 Gy). Hyperpigmentation: common in darkly pigmented skin. Acute: mild erythema, desquamation. Late: telangiectasia, atrophy at higher doses.
Conclusions
A BED of ~30–40 Gy (using α/β 10) is the threshold for effective keloid prevention after surgery. Single-fraction doses of 10–15 Gy or 15 Gy/3 fractions are practical regimens achieving this BED with acceptable toxicity. Higher BED does not proportionally improve recurrence control once the threshold is reached.
Key Limitations
Key Limitations: Meta-analysis of heterogeneous retrospective studies with different RT timing, techniques, and follow-up. α/β ratio for keloids is unknown — assumed 10 Gy based on late-responding tissue models. Study quality is low across the evidence base. Publication bias toward positive results is likely.
Clinical Context
BED-based dosing informs current keloid RT practice. Recommended regimens: 15–20 Gy in 3–5 fractions (BED 30–40 Gy) initiated within 24 hours of surgical excision. Delaying RT >24 hours post-excision significantly increases recurrence. Sternal, anterior chest, and deltoid keloids have highest recurrence rates and may require higher doses.
References