2022-RA-721-ESGO Clinical outcomes of SBRT boost to the cervix as an alternative to intracavitary brachytherapy in locally advanced cervical cancer: Retrospective analysis from the West of Scotland

Introduction/Background

Concurrent chemoradiotherapy (CCRT) combined with image guided brachytherapy (IBGT) is the international gold standard management for locally advanced cervical cancer. ESTRO guidelines recommend aiming for EQD₂ of 85–90Gy to the cervix, in order to achieve local control rate of >90%. Associated G3–5 morbidity is up to 5–10%, with fistula incidence <5%. However, a proportion of patients are ineligible for IGBT and a standard photon boost is suboptimal. We evaluated the indications for SBRT boost at our institution and the resultant local control/toxicity outcomes.

Methodology

The central radiotherapy prescribing system at a single institution was interrogated to identify patients with locally advanced cervical cancer who received SBRT boost to cervix in addition to or as a replacement for IBGT, from 1st July 2017 to 31st January 2021.

Results

17 patients were identified; median age was 68 years (range 32–77) and median follow up was 17 months. FIGO 2009 stage distribution was II (8/17), III (7/17), and IV (2/17). Mean tumour size was 4.5 cm. Indication for SBRT consisted of: medical contra-indication (9/17), unfavourable anatomy (5/17), and patient refusal (3/17). Median dose of external beam was 45Gy in 25 fractions (range 43–50Gy). SBRT boost PTV was delineated on CT (cervix and gross residual disease with a 4–5 mm margin), aiming for 24–28Gy in 4 fractions (range 7–28Gy). Median cumulative EQD₂ (a/β= 10) was 75.2Gy (range 58–91), and median SBRT PTV size was 54 cm³ (range 12–126). Local control rate was 15/17 (88.2%). G3 toxicity occurred in 2/17 (11.8%); one rectovaginal-vaginal and one vesico-vaginal fistula (the latter had progressive disease). No G4–5 toxicity was reported.

Conclusion

SBRT boost was effective and tolerable in this cohort, but EQD₂ of 85–90Gy was not achieved in majority of cases. MRI based planning may improve target delineation and a consensus guideline on appropriate constraints would be advantageous.