Introduction/Background In Luxembourg, brachytherapy (BT) is not widely available. The focus of this research was to assess the feasibility, safety, and efficacy of Stereotactic Body Radiation Therapy (SBRT) as a boost in locally advanced cervical cancer.

Methodology Between 2017–2019, patients with histologically proven FIGO (2018) stages IB-IVA treated by external radiotherapy (VMAT): 50 Gy in 28 fractions to the pelvic +/- lomboaortic lymph nodes and 60.04 Gy using a simultaneous integrated boost to the macroscopic tumor +/- positive FDG-PET-CT scan nodes were included. Concurrent weekly cisplatin (40 mg/m²) was given. Following concurrent radio-chemotherapy (CCRT), a pelvic computed tomography scan with a magnetic resonance imaging simulation were performed within the 1st week after CCRT. Target volumes (GTV-T, HR-CTV, PTV) and organs at risk (bladder, rectum, sigmoid, and bowel bag) were define on the MRI. The boost prescription was 13Gy in two fractions delivered in two consecutive days. SBRT boost was delivered using a Cyberknife^®M6 and tracking based fiducial markers. A 12-week MRI and Pet-Ct were used to determine the therapeutic outcomes.

Results Eleven patients were included, median age was 59 years (57–68), 100% had a squamous cell carcinoma, 45% had a stage ≥ IIIC. The median overall treatment time was 52 days (Q1–3: 49.5–56). With a median follow up of 20 months (12.5–31), the local control was 73%. Three patients relapsed: external parametrial areas (n=2), pre-sacral node (n=1). No acute genito-urinary toxicity (Grade > II) was observed, 18% had acute grade III gastrointestinal toxicity. The most common long-term toxicity were grade I-II genito-urinary and gastro intestinal, no Grade ≥ III was observed. Progression free survival during the median follow-up of 20 months was 71.7%.

Conclusion SBRT boost seems feasible and well tolerable, although it cannot substitute BT. Further studies with longer follow-up periods are warranted to confirm long-term outcomes.