PO47

Abstract

Purpose High-dose-rate (HDR) brachytherapy is a vital part of treatment in patients with locally advanced cervical cancer. Current guidelines recommend the use of image-guided adaptive brachytherapy (IGABT). Several fractionation schedules are used in external beam radiotherapy (EBRT) and brachytherapy (BT). A retrospective analysis of patients treated with radio(chemo)therapy and HDR brachytherapy due to cervical cancer was conducted. We compared the efficacy of two fractionation schedules implemented in our department. Materials and Methods Schedule one ("5x6 Gy") consisted of five fractions of 6 Gy delivered within 2.5 weeks. In the majority of patients, the dose was prescribed to point A. Schedule two ("4x7 Gy") consisted of four fractions of 7 Gy delivered within two weeks. In all patients, the dose was prescribed to CTV. Local control (LC) and distant metastasis-free survival (DMFS) were calculated. The Kaplan-Meier estimator, log-rank and Mann-Whitney U test were used in statistical analysis. One hundred seventeen patients were included in this analysis. Median age was 57 years (range: 29 - 79). The disease stage was re-assessed according to FIGO 2018 classification. Forty-five percent of patients had FIGO IIIC1 disease, 29% - FIGO IIIB, 15% - FIGO IIB and 6% - FIGO IIIC2. The vast majority of patients (96%) had were diagnosed with planoepithelial carcinoma, 2,5% with cervical adenocarcinoma, one patient with clear cell carcinoma and one with serous carcinoma. The "5x6 Gy" fractionation was administered in 79% of patients. The median overall treatment time (OTT) was 58 days (range: 45 - 139 days). The median CTV D90 EQD2 sum of EBRT and BT was 89 Gy (range: 65 - 114 Gy). Results In the "5x6 Gy" subgroup, the follow-up was significantly longer (p=0.00006), CTV D90 EQD2 was significantly higher (p=0.0001), and OTT was significantly longer (p=0.02). No other significant differences were observed between the subgroups. They were well balanced in terms of patients' age (p=0.6), histopathological grade of the tumour (p=0.2) and FIGO stage (p=0.07). In the whole group, 5-year LC was 91%, 5-year regional nodal control was 86%, and 5-year DMFS was 80%. The comparison of the two fractionation schedules ("5x6 Gy" vs "4x7 Gy") revealed that higher CTV D90 EQD2 was not associated with better local or distant control. There were no differences in LC (p=0.79), regional nodal control (p=0.7) or DMFS (p=0.83) between the subgroups. However, better regional nodal control and longer DMFS were observed in patients with OTT≤60 days (p=0.035 and p=0.017, respectively). Conclusions Both fractionation schedules have similar efficacy. A shorter overall treatment time is associated with better regional nodal control and DMFS. However, a longer follow-up is needed to confirm these findings. High-dose-rate (HDR) brachytherapy is a vital part of treatment in patients with locally advanced cervical cancer. Current guidelines recommend the use of image-guided adaptive brachytherapy (IGABT). Several fractionation schedules are used in external beam radiotherapy (EBRT) and brachytherapy (BT). A retrospective analysis of patients treated with radio(chemo)therapy and HDR brachytherapy due to cervical cancer was conducted. We compared the efficacy of two fractionation schedules implemented in our department. Schedule one ("5x6 Gy") consisted of five fractions of 6 Gy delivered within 2.5 weeks. In the majority of patients, the dose was prescribed to point A. Schedule two ("4x7 Gy") consisted of four fractions of 7 Gy delivered within two weeks. In all patients, the dose was prescribed to CTV. Local control (LC) and distant metastasis-free survival (DMFS) were calculated. The Kaplan-Meier estimator, log-rank and Mann-Whitney U test were used in statistical analysis. One hundred seventeen patients were included in this analysis. Median age was 57 years (range: 29 - 79). The disease stage was re-assessed according to FIGO 2018 classification. Forty-five percent of patients had FIGO IIIC1 disease, 29% - FIGO IIIB, 15% - FIGO IIB and 6% - FIGO IIIC2. The vast majority of patients (96%) had were diagnosed with planoepithelial carcinoma, 2,5% with cervical adenocarcinoma, one patient with clear cell carcinoma and one with serous carcinoma. The "5x6 Gy" fractionation was administered in 79% of patients. The median overall treatment time (OTT) was 58 days (range: 45 - 139 days). The median CTV D90 EQD2 sum of EBRT and BT was 89 Gy (range: 65 - 114 Gy). In the "5x6 Gy" subgroup, the follow-up was significantly longer (p=0.00006), CTV D90 EQD2 was significantly higher (p=0.0001), and OTT was significantly longer (p=0.02). No other significant differences were observed between the subgroups. They were well balanced in terms of patients' age (p=0.6), histopathological grade of the tumour (p=0.2) and FIGO stage (p=0.07). In the whole group, 5-year LC was 91%, 5-year regional nodal control was 86%, and 5-year DMFS was 80%. The comparison of the two fractionation schedules ("5x6 Gy" vs "4x7 Gy") revealed that higher CTV D90 EQD2 was not associated with better local or distant control. There were no differences in LC (p=0.79), regional nodal control (p=0.7) or DMFS (p=0.83) between the subgroups. However, better regional nodal control and longer DMFS were observed in patients with OTT≤60 days (p=0.035 and p=0.017, respectively). Both fractionation schedules have similar efficacy. A shorter overall treatment time is associated with better regional nodal control and DMFS. However, a longer follow-up is needed to confirm these findings.