Comparative Effectiveness of External Beam Radiation Therapy Versus Brachytherapy for T1-2 Non-melanoma Skin Cancer

Abstract

Definitive external beam radiation therapy (EBRT) and brachytherapy (BT) are treatment options for the management of T1-2 squamous cell carcinomas (SCC) and basal cell carcinomas (BCCs) of the skin. The purpose of this analysis is to review the published literature of the two techniques and compare cosmesis and tumor control outcomes. The hypothesis is that cosmesis and tumor control of EBRT and BT for indolent skin cancers are similar. We performed a meta-analysis, combining studies published from 1985 to 2016, including patients with T1-2 N0 SCCs or BCCs treated with definitive EBRT or BT and ≥12 months follow-up. Data were abstracted from individual fractionation arms within each study. The primary endpoint was post-treatment cosmesis, rated as “good,” “fair,” or “poor,” and secondary endpoint was local recurrence (LR). Biologically equivalent doses were calculated, where α/β = 3, for late toxicity/cosmesis (BED3). Weighted linear regression models were used to estimate linear relationships between BED3and the observed percentages of patients experiencing cosmetic outcomes with 95% confidence intervals (CIs). The 1-year and 5-year LR rates were recorded. A total of 24 studies with 10,186 patients were included; of these, 9,581 patients received EBRT and 605 received BT. Among the ten studies with cosmetic data, 2,229 patients received EBRT and 454 received BT. Median follow-up was 36 months (range: 12 – 77); for EBRT it was 36 months (range: 18 – 77), and for BT it was 30 months (range: 12 – 66). Median dose was 45 Gy/10 fractions (interquartile range [IQR]: 36 Gy/5-55 Gy/16.8) at 4.4 Gy/fraction (IQR: 3 – 6.9 Gy); the most hypofractionated was 28 Gy/1. The mean age was 73 years (range: 62-84). Cosmetic results from BEDs representative of the dose fractionation spectrum are shown in the Table. Good and fair cosmesis were similar at BED3 of 80 for BT and EBRT. Good cosmesis was more frequently observed in patients receiving BT vs EBRT at BED3 of 120: 99% (95% CI: 90-100%) vs 68% (95% CI: 60-74%), p<0.05. Fair cosmesis was more frequently observed in patients receiving EBRT vs BT at BED3 of 120: 22% (95% CI: 18-28%) vs 4% (95% CI: 0-9%), p<0.05. Poor cosmesis was noted in <10% of patients for EBRT and BT for any BED3 (p>0.05). LR was <7% for both at one year; there was too few events to evaluate BT at a longer time point.Abstract 3805; Table 1Cosmesis outcomes of BT vs. EBRTGood cosmesisFair cosmesisPoor cosmesisBED3=80BED3=100BED3=120BED3=80BED3=100BED3=120BED3=80BED3=100BED3=120BT94% (82-100%)95% (88-100%)*99% (90-100%)*4% (0-10%)3% (0-9%)2% (0-9%)*5% (0-9%)5% (0-7%)4% (0-8%)EBRT79% (60-95%)79% (60-82%)*68% (60-74%)*12% (0-31%)18% (8-31%)22% (18-28%)*10% (1-18%)8% (2-12%)5% (1-7%)Note: * denotes p-value < 0.05 for BT vs. EBRT, 95% CI in parentheses. Open table in a new tab Note: * denotes p-value < 0.05 for BT vs. EBRT, 95% CI in parentheses. Cosmesis and cancer control of BT and EBRT for skin BCCs/SCCs are generally similar, with increased “fair” cosmesis (over “good” cosmesis) seen in EBRT at higher BEDs. Poor cosmesis is rare for either modality.