PET CT Based Stereotactic Body Radiosurgery (SBRT) in Non-Metastatic Cervical Cancer. The First Bolivian Experience.

PURPOSE/OBJECTIVE(S) Incidence and mortality rates of cervical cancer in Bolivia are the highest in Latin America. Therapeutic failure is frequent due to economic, cultural, and social barriers. Stereotactic Body Radiosurgery (SBRT) is an alternative in patients not suitable for brachytherapy (BCT). This study aimed to report the first Bolivian experience in Cervix SBRT in 3 different scenarios: 1. Local consolidation as an alternative of BCT, 2. Relapse after surgery and 3. Relapse after radiotherapy (reirradiation). MATERIALS/METHODS We retrospectively analyzed 11 patients treated with SBRT between July 2019 to July 2020. VMAT-IGRT technique with FDG PET/CT simulation, for planning was performed to add biological information in defining the gross tumor volume (GTV). Foley catheter (150ml) and a vaginal immobilization device designed in 3D Acrylonitrile Butadiene Styrene were installed. GTV-T (MTV), (Metabolic tumor Volume), was contouring according to hypermetabolic PET CT scan by semi-quantitative method. We added a PTV margin of 3-5mm, PTV Opti (-3mm) to critic structures like rectal, bladder and small bowel. The total dose to GTV-T was 21 Gy/3 fx, 18 Gy /3 fx and 30 Gy/5 fx respectively. The equivalent dose in 2 Gy (EQD210-3) was reported for tumor control and OAR restrictions. Gastrointestinal (GI) and genitourinary (GU) toxicity were reported according to RTOG criteria. Quality of life (QoL) was assessed with EORTC C-30/C-24 scale, at the beginning, at the end of treatment and every third month. We used Chi-square and ANOVA for statistical analysis. RESULTS Five patients were including in group 1, four in group 2, and two in the re- irradiation group. Mean follow-up was 13 months (7-19), mean age 49 years (31-82), ECOG 0-1 (91%). Mean GTV-T (MTV), volume was 31, 37 and 70 cc, respectively. Mean dose (EQD210) was 82, 78 and 127 Gy. Mean (EQD3) doses rectum/bladder (D2cc) in group 1 (75/84 Gy), group 2 (73/79 Gy) and group 3 (101/109 Gy). Mean SUV-Max was 6 (4-9). One-year OS 82% (9), PET negative at 4 months 82%, LC 100% group 1 and 2 but 50% in group 3. Three patients (33%) progressed systemically. No chronic G2 or G3 GI or GU toxicity was reported, three patients reported mild rectal bleeding (G1). No relationship between biological doses (EQD210-3) and rectum (P = 0.65) or bladder (P = 0.27) chronic toxicity were found. No significant differences in global QoL. CONCLUSION We believe SBRT in non-metastatic cervical cancer in patients no suitable to BCT or salvage scenario is an excellent alternative with high rates of LC and low chronic toxicity without a detriment of QoL. We also affirm that RT guided by FDG-PET CT is reliability and accurate for tumor delineation and useful at the end of treatment to characterize residual disease. These results should be confirmed with a larger sample.