KEY POINTS
- The systematic review searched five databases for comparative studies published from 2014 through 2025. It included 11 studies: nine dosimetric comparisons, one population-based cohort and one consensus guideline, mainly involving locally advanced cervical cancer.
- Brachytherapy consistently produced greater central dose escalation. In one comparison, high-risk clinical target volume D50 was 12.1 Gy per fraction with intracavitary/interstitial brachytherapy versus 9.93 Gy with SBRT; another reported cumulative D50 of 42.08 versus 32.94 Gy (p < 0.001).
- SBRT sometimes produced higher D90, D95 or D98 and better conformity, particularly when plans were generated without a planning target volume margin. These peripheral-coverage advantages did not reproduce the 150–250% intratumoral hotspots characteristic of brachytherapy.
- The effect of realistic margins was substantial. In a magnetic resonance-guided adaptive comparison, total high-risk clinical target volume D90 was 95.6 Gy EQD2 with margin-free SBRT but fell to 82.9 Gy after a planning target volume margin was applied, compared with 89.7 Gy using brachytherapy.
- Organ-at-risk results were inconsistent. Some margin-free SBRT comparisons reduced bladder, rectal and sigmoid doses by 20–30%, while another found lower cumulative bladder and sigmoid doses with brachytherapy: 74.6 versus 84.7 Gy and 67.9 versus 75.75 Gy, respectively.
- Attempting brachytherapy-like central escalation with external-beam treatment could violate organ constraints. One highly heterogeneous robotic SBRT strategy produced a bladder D2cm³ of 172.7 Gy and was judged clinically infeasible.
- The only survival analysis included 15,905 patients, of whom 90.5% received brachytherapy and only 0.8% SBRT. Unadjusted median overall survival was 99.1 versus 30.3 months, but after propensity matching the difference was not significant (hazard ratio 1.477; 95% confidence interval, 0.746–2.926; p = 0.263).
- Most SBRT plans were retrospective simulations rather than delivered treatments. Comparative late toxicity, patient-reported outcomes and quality-of-life data were insufficient, and the heterogeneity of schedules and planning methods prevented meta-analysis.
CLINICAL TAKEAWAY
Brachytherapy remains the reference boost technique for curative gynecologic radiotherapy because it delivers central dose escalation that external-beam SBRT cannot reliably reproduce while accounting for pelvic motion. SBRT is a fallback for patients in whom brachytherapy is genuinely impossible, not an equivalent non-invasive replacement supported by the current evidence.