ESTRO 2023 - Abstract Book

S312

Sunday 14 May 2023

ESTRO 2023

Conclusion The greatest mean increase in dose to bladder occurred with displacements anteriorly and to rectum and bowel posteriorly, in keeping with anatomical locations. Applicator displacements as small as 1 mm can result in increases in D2cc of >5% and dosimeters should have the ability to detect displacements at least as small as this. The effect of applicator displacements on bladder and rectum subsections is important for determining the optimal positions for dosimeters. PD-0409 Radio-chemotherapy and interventional radiotherapy in vaginal carcinoma: a monocentric experience V. Lancellotta 1 , G. Macchia 2 , B. Fionda 1 , R. Autorino 1 , M. Campitelli 1 , M. De Angeli 3 , G. Garganese 4 , B. Gui 5 , L. Russo 6 , S. Fragomeni 7 , G. Ferrandina 8 , M.A. Gambacorta 1 , L. Tagliaferri 1 1 Fondazione Policlinico Universitario A. Gemelli IRCCS, Dipartimento di Diagnostica per Immagini, Radioterapia Oncologica ed Ematologia, Rome, Italy; 2 Gemelli Molise Hospital – Università Cattolica del Sacro Cuore, Radiation Oncology Unit, Campobasso, Italy; 3 Università di Roma, Tor Vergata, Radiation Oncology, Rome, Italy; 4 Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Roma, Department of Medicine and Health Sciences, Rome, Italy; 5 Fondazione Policlinico Universitario A. Gemelli IRCCS, Dipartimento Diagnostica per Immagini, Radioterapia Oncologica ed Ematologia, Rome, Italy; 6 Dipartimento Diagnostica per Immagini, Radioterapia Oncologica ed Ematologia, Dipartimento Diagnostica per Immagini, Radioterapia Oncologica ed Ematologia, Rome, Italy; 7 Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Department of Medicine and Health Sciences, Rome, Italy; 8 Department of Medicine and Health Sciences, Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Rome, Italy Purpose or Objective Vaginal carcinoma (VC) is a rare malignancy accounting for 1% to 2% of all gynaecologic cancers. Although surgery yields good local control (LC) and overall survival (OS) in selected cases of vaginal intraepithelial neoplasms and early (I–II) stages of VC, definitive radio-chemotherapy (RCT) followed by interventional radiotherapy (IRT, also called brachytherapy, BT) is considered an excellent option. The aim of this study was to report the results of our mono-institutional series of vaginal cancer patients treated with radio-chemotherapy followed by image- guided IRT. Materials and Methods We retrospectively analysed 16 patients with primary vaginal cancer who received RCT followed by IRT with curative intent between January 2019 and December 2021. OncentraBrachy treatment planning system and a Flexitron (Elekta, Stockholm, Sweden) device with a 192-Ir source were used for IRT treatment. The primary study endpoint was the local control (LC), secondary endpoints were the overall survival (OS), the cancer specific survival (CSS), disease free survival (DFS) and the rate and severity of acute and late toxicities. Results All patients received planned treatment. Twelve patients were stage II, 2 patients’ stage III and 2 stage IVB (International Federation of Gynecology and Obstetrics stages 2008). The median total dose of external beam RT was 45Gy (range 45Gy- 60Gy). The IRT total dose was 28 Gy. All patients received weekly cisplatin chemotherapy. The median duration of follow- up was 19 months (6-38 months). One-year LC, OS, CSS and DFS rates were 100%, 100%, 100%, 92.8%, respectively. Acute toxicity was registered in 10 cases. There were five gastro/genitourinary G1, four gastrointestinal G2, one genito-urinary G2, three vaginal inflammatory G2. Late toxicity was reported in ten cases: 6 G1 stenoses, 2 G2 stenoses, and 1 G3 stenosis. Teleangectasia G1 was identified in one case. Conclusion The combination of definitive RCT with image-guided IRT is a successful therapeutic option for primary vaginal cancer with a manageable level of toxicity. PD-0410 The benefits of CT-guided freehand interstitial brachytherapy for cervical cancer X. Yang 1 , Z. Li 1 , J. Fu 1 1 Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Radiation Oncology, Shanghai, China Purpose or Objective We aim to investigate the dosimetric difference between computed tomography (CT) guided freehand interstitial brachytherapy and conventional point A plan (CP) in the treatment of cervical cancer. Materials and Methods Thirty-five cervical cancer patients who received intracavitary brachytherapy combined with interstitial brachytherapy were selected. Each patient received five fractions of brachytherapy. During the brachytherapy, the uterine tube and two implantation needles were first placed by freehand, and then the first CT scan was performed. Increase the number of implanted needles and adjust the direction and depth of the implantation needles according to the CT images. CT scans were performed again and transferred to the Oncentra planning system for delineation and planning. High-risk clinical target volume (HR-CTV), point A, and organs at risk were delineated. Results According to the coverage index (CI) of CPs’ plans, group A (CI ≥ 0.90) contained 42 CPs and related image-guided adaptive brachytherapy (IGABT) plans, and group B (CI <0.90) contained 133 CPs and corresponding IGABTs’ plans. The HRCTV volume and tumor diameter in group A were significantly smaller than in group B (45.2 cm3 VS 63.7 cm3, P < 0.001 and 3.3 cm VS 4.6 cm, P < 0.001). IGABT significantly improved overall and group B D90 and CI, decreased bladder dose, decreased sigmoid dose in group A, and improved dose conformity and uniformity. Conclusion IGABT can improve target coverage, dose conformity, and uniformity. It protects organs at risk, and has advantages for patients with larger tumors.