ESTRO 2021 Abstract Book

S1066

ESTRO 2021

Results Thirty-eight patients were analysed from January 2020 to July 2020. The median age was 56 years (range 32- 81). Twenty-three (60.5%) had Stage IIIC, two (5.3%) Stage IIIB and 13 (34.2%) Stage IIB. Complete response was achieved in 23 (63.8%) of 38 patients at three months assessment and 33 (91.6%) of patients at six months assessment. Ten (26.3%) of 38 patients, who were not in complete clinical response at the first assessment, achieved a complete clinical response thereafter. Three patients after 6 months reported a further reduction of residual disease while two patients had a stable partial response. Conclusion Our data seem to suggest that 6 months from the end of treatment could be a reasonable time for clinical response assessment in LACC patients. This longer timeline could include patients not yet responders after 3 months, avoiding too early rescue therapies. Further and larger studies are needed to confirm this finding. PO-1295 Stereotactic ablative body radiotherapy boost for cervical cancer when brachytherapy is not feasible T.H. Lee 1 , I.A. Kim 2 , J. Kim 2 , C. Song 2 , Y.B. Kim 3 , K. Kim 3 , J.H. No 3 , D.H. Suh 3 , J. Chung 2 , K. Eom 2 1 Seoul National University Hospital, Department of Radiation Oncology, Seoul, Korea Republic of; 2 Seoul National University Bundang Hospital, Department of Radiation Oncology, Seongnam, Korea Republic of; 3 Seoul National University Bundang Hospital, Department of Obstetrics and Gynecology, Seongnam, Korea Republic of Purpose or Objective The purpose of this study was to analyze the treatment efficacy and safety of stereotactic ablative body radiotherapy (SABR) boost for cervical cancer patients not amenable to brachytherapy. Materials and Methods A retrospective review of the medical records of 25 eligible patients was performed. The patients underwent pelvic radiotherapy in 25 or 28 fractions with a median dose of 45 Gy (range, 44–50.4 Gy). SABR boost was delivered after pelvic radiotherapy, with a median dose of 25 Gy (range, 20 to 33 Gy), and a median fraction number of 5 (range, 4–6). Patients with a follow-up period of more than one year were included in the toxicity analysis, and hematuria and hematochezia that occurred later than 3 months after the radiotherapy were The median follow-up period after RT was 2.85 years (range, 0.33 to 6.60). The 3-year local control, locoregional control, disease-free survival, and overall survival rates were 80.9%, 75.8%, 40.9%, and 77.1%, respectively. The 3-year rates of freedom from hematuria and hematochezia were 58.5% and 29.6%, respectively. No grade 4–5 toxicity was reported. Receiver operating characteristic (ROC) curve analysis showed that simple summation of the mean biologically equivalent dose (BED) to the bladder was predictive of hematuria (p = 0.040), while the simple summation of the maximum BED to the rectum was marginally predictive of hematochezia (p = 0.057). Conclusion SABR boost for cervical cancer was effective and tolerable. Although it cannot substitute brachytherapy, it can be a treatment option when brachytherapy is not possible. graded. Results PO-1296 Usage of PET/CT as a post-treatment surveillance strategy in locoregionally advanced cervical cancer N. Cihoric 1 , H. Astrid Elisabeth 1 , S. Imboden 2 , D. Aebersold 3 , M. Blatti 1 , A. Tsikkinis 4 , L. Kristina 3 1 Inselspital, Bern University Hospital and University of Bern, Department of Radiation Oncology, Bern, Switzerland; 2 Inselspital, Bern University Hospital and University of Bern, Department of Obstetrics and Gynecology, Bern, Switzerland; 3 Inselspital, Bern University Hospital and University of Bern, Department of Radiation Oncology Bern, Switzerland, Bern, Switzerland; 4 German Oncology Center, Limassol, Cyprus, Department of Radiation Oncology, Limassol, Cyprus Purpose or Objective Optimal follow-up strategies for post treatment surveillance in patients with cancer of the uterine cervix treated with radiochemotherapy are unknown. Our institution standardized posttreatment surveillance with the introduction of a 18F-FDG/PET-CT (PET/CT) 6 months after treatment. This retrospective study aimed to evaluate the impact of institutional strategy with post-treatment PET/CT surveillance. Materials and Methods From November 2011 to March 2019, one hundred and sixty-one patients with locoregionally advanced cervical cancer (FIGO IA2 - FIGO IVA) were treated with external beam radiochemotherapy (EBRCT) in 10 Swiss institutions. Upon completion, patients were referred to the University Hospital of Bern Inselspital for further treatment with HDR intrauterine brachytherapy. In our discharge summary, besides a clinical examination every three months for the first two years after treatment and every six months afterwards, a posttreatment PET/CT at six months was recommended. We have reviewed treatment charts, PET/CT reports, posttreatment clinical summaries, and other related medical data for all patients. Inclusion criteria for our study were a PET/CT within one year and sufficient clinical documentation. The primary goal of the study was to evaluate the impact of PET/CT findings. Results In fifty-eight (57%) patients, there was no significant activity of 18F-FDG detected by PET/CT, while substantial activity was detected in forty-four (43%) patients. In 38 (86%) patients cancer recurrence was suspected. Systemic metastasis was the most common site of failure (n=27, 61%), followed by pelvic nodal recurrence (n=6, 16%) and local relapse (n=5, 11%). In 6 (14%) patients, findings did not correlate with cervical cancer recurrence. The Median follow-up time for patients with positive PET/CT findings was 18 months, ranging from 2 to 107 months. Positive PET/CT results initiated further procedures in 38 patients (86%).