ESTRO 2021 Abstract Book

S647

ESTRO 2021

We evaluated 66 patients treated between August 2015 and November 2019 who underwent pretreatment staging, subsequent midtreatment evaluation, and definitive restaging 3 months after completing the whole treatment, all using PET/MRI. The pretreatment parameters (pre-SUVmax, pre-SUVmean, pre-MTV, pre-MTV- S, pre-TLG, pre-TLG-S), and the midtreatment parameters at week 5 during chemoradiotherapy (mid-SUVmax, mid-SUVmean, mid-MTV, mid-MTV-S, mid-TLG and mid-TLG-S) were recorded. The value of ADC was also measured. Furthermore, we recorded absolute and relative changes in all parameters - Δ and Δ%. We divided the whole group of patients into “responders” (CMR) and “non-responders” (non-CMR), and compared them on the basis of the parameters from pre-PET/MRI and mid-PET/MRI. Results A statistically significant difference in the evaluated parameters between responders and non-responders was found for the following parameters: mid-MTV, mid-TLG, mid-TLG-S, mid-MTV-S, mid-tumor size, and Δ%SUVmax. According to the ROC analysis, mid-MTV-S showed the best albeit moderate discrimination ability for the prediction of non-CMR. Significant mutual correlations of all variables, in particular between mid-MTV- S and mid-TLG-S and between mid-MTV and mid-TLG, were found (all p<0.05). Conclusion Our study confirmed that when using the midtreatment PET/MRI we are able to identify parameters having the discrimination ability for the prediction of non-CMR. In particular mid-MTV-S, mid-MTV, mid-tumor size, mid- TLG-S, mid-TLG and Δ%SUVmax. PD-0815 Prognostic role of early FDG-PET/CT in locally advanced cervical carcinoma (LACC) patients G. Vullo 1 , V. De Sanctis 1 , D. Anzellini 2 , G. Facondo 3 , R.C. Sigillo 2 , D. Prosperi 4 , D. Riolo 5 , M.F. Osti 2 1 Sapienza Università di Roma, AOU Sant'Andrea Roma, UO Radioterapia Oncologica, ROMA, Italy; 2 Sapienza Università di Roma, AOU Sant'Andrea Roma, UO Radioterapia Oncologica, Roma, Italy; 3 Sapienza Università di Roma, AOU Sant'Andrea Roma, UO Radioterapia Oncologica, , Roma, Italy; 4 Sapienza Università di Roma, AOU Sant'Andrea Roma, UOC Medicina Nucleare, Roma, Italy; 5 Sapienza Università di Roma, AOU Sant'Andrea Roma, UOC Medicina Nucleare, , Roma, Italy Purpose or Objective To evaluate in patients with LACC the prognostic impact of FDG-PET/CT (early-PET) after exclusive chemoradiotherapy (CRT) and before intra-uterine brachitherapy Materials and Methods We included 23 pts with LACC (range 30-75 years) that referred to our institution between 2013 and 2019. Pts were treated with concomitant CRT and subsequent brachytherapy. FIGO STAGE: 1/23 were IIA, 12/23 IIB, 4/23 IIIB, 4/23 IIIC and 2/23 IVA. 9/23 pts had regional lymph node involvement and 2 pt had also positive lombo-aortic lymph nodes. 20/23 pts underwent radiotherapy and concomitant weekly chemotherapy with Cisplatin (40mg/mq2), 4 pts received neoadjuvant chemotherapy and 1 patients only radiotherapy. 19/23 pts were treated with IMRT tecnique and 17 of them received IMRT-SIB (2.2 Gy x 28 fractions on GTV-cervix and GTV-LNs PET-positive, 1.8 Gy x 28 fraction on pelvis ± LN lombo-aortics). The total brachytherapy dose was 21 or 28 Gy in 3-4 fractions, 7 Gy per fraction, with the aim to obtain a total dose (EBRT plus BT) in the range of 85-90 Gy (6 pt 28 Gy, 17 pt 21 Gy). All pts performed FDG-PET/CT after CRT and before brachytherapy (early- PET). PET images were rated as positive when there was focal uptake with a SUV max >3. Results At the end of CRT and before brachytherapy all pts performed early-PET: 14/23 were negative and 9/23 positive. - 2/14 (14.3%) pts with negative early-PET showed a progressive/relapse disease: 1 systemic (lung-bones) progressive disease and 1 cervical, annexial and nodal relapse after 9 months from the end of brachytherapy. - 5/9 pts (55%) with positive early PET-TC had progressive/relapse disease: 4 pts showed systemic (lung-bones) progressive disease and 1 pt showed nodal, cervical and bone relapse after 18 months from the end of brachytherapy. Conclusion Our preliminary results showed that early-PET before brachytherapy could have a predictive value in assessing the risk of recurrence/progression in LACC pts. Pts with positive early-PET may benefit from adjuvant systemic treatment. PD-0816 Retrospective validation of coverage probability based SIB-N in LACC: a mono-institutional analysis A. Kedves 1,3,4 , C. Glavak 1 , G. Antal 1 , G. Toller 1 , Z. Volgyi 1 , A. Faour 1 , B. Petrasi 1 , A. Gulyban 2 , F. Lakosi 1 1 Somogy County Kaposi Mór Teaching Hospital, Dr. József Baka Center, Department of Radiation Oncology, Kaposvar, Hungary; 2 Medical Physics Department, Institut Jules Bordet, Bruxelles, Belgium; 3 Institute of Diagnostics, Faculty of Health Sciences, University of Pécs, Kaposvar, Hungary; 4 Doctoral School of Health Sciences, University of Pécs, Pecs, Hungary Purpose or Objective To retrospectively validate Coverage probability (CovP) based simultaneous integrated nodal boost (SIB-N) concept introduced by the EMBRACE group in locally advanced cervical cancer (LACC) in terms of dosimetry, treatment verification and clinical outcome. Materials and Methods Between 01/2016 and 09/2020 twenty-six node-positive FIGO stage ≥1B2 LACC patients (pts) were treated with external beam radiotherapy (EBRT) with concurrent chemotherapy followed by image-guided adaptive brachytherapy (IGABT). The treatment consisted of 45 Gy to the entire pelvis or pelvis+paraaortic (58% of cases) (PAO) region with 55/57.5 Gy SIB-N using volumetric arc therapy with online CBCT verification. Contouring and planning followed the EMBRACE 2 protocol. The boosted nodes were contoured on each CBCT and were assessed for coverage by the PTV-N. In patients with ≥Gr.3 non-hematologic side effect both EBRT