ESTRO 2020 Abstract Book

S596 ESTRO 2020

Results Five-year actuarial OS, DFS and locoregional control rates were 80%, 82% and 86%,respectively, with a median follow- up time of 51 months (Range 4-96 months). Forty-eight patients experienced a recurrence, 80% of which included distant disease. In-field recurrence rate was 11.7%. Using the new FIGO staging, 48% of patients were upstaged to IIIC. Compared to FIGO 2009, OS and DFS were higher for all 2018 FIGO stages. Five-year OS was 100% for early stage disease (IA1-IIA2) comparatively to 83.0%, 72.7% and 62.5% in node-negative locally advanced disease, IIIC1 and IIIC2 stages, respectively (p<0.0001). Conclusion Integration of state-of-the-art imaging in cervical cancer staging as well as in radiotherapy and brachytherapy planning leads to excellent oncologic outcomes, however distant recurrence remains an important issue. FIGO 2018 staging better reflects patient prognosis, highlighting the need for new treatment strategies in stage IIIC cervical cancer. PO-1129 Impact of individualized ITV margins for IMRT of cervical cancer on target coverage K. Wada 1 , E. Nakanishi 1 , M. Toratani 1 , T. Ikawa 1 , N. Kanayama 1 , M. Morimoto 1 , K. Konishi 1 , T. Teshima 1 1 Osaka International Cancer Institute, Radiation Oncology, Osaka, Japan Purpose or Objective Intensity-modulated radiation therapy (IMRT) for cervical cancer has high dose conformality and normal tissue sparing. Daily target motion caused by variation in bladder and rectal filling could cause insufficient target coverage. Generating individualized internal target volumes (iITVs) from CT simulation and pretreatment diagnostic images can manage target motion. However, practical and quantitative research on this approach are lacking. We assessed whether an individualized approach improves target coverage without increasing irradiated bowel volume compared to the conventional approach. Material and Methods We retrospectively analyzed 23 patients who underwent definitive treatment with IMRT for cervical cancer from January 2017 to July 2019. Target volume was defined as the gross tumor volume plus remaining cervix and body of uterus. Various isotropic margins (5, 10, 15, 20, and 25 mm) were added to the target volume, delineated from CT simulation and pretreatment bone registration images, to generate iITVs (iITV-x, x=5, 10, 15, 20, and 25), whereas conventional ITVs (cITV-x, x=5, 10, 15, 20, and 25) were generated solely from CT simulations. ITVs were modified to avoid muscles and bony boundaries and expanded by a 5-mm margin for planning target volumes (PTVs) (iPTV-x and cPTV-x, x=5, 10, 15, 20, and 25). Target coverage was evaluated using cone-beam CT (CBCT) for daily setup. The bowel bag volume overlapping PTVs was evaluated as a surrogate for the volume of irradiated bowel. The correlations between the percentage of off-target fractions and factors such as tumor volume and standard deviations (SD) of rectal and bladder volumes on CT simulation and pretreatment images were analyzed. Results In total, 463 CBCTs were evaluated. The result of per fraction analysis is shown in the table. To obtain >90% target coverage, cITV-20 or iITV-10 were necessary. The mean PTV volumes and the overlapping bowel bag volumes of cPTV-20 vs. iPTV-10 were 979.2 cc vs. 731.1 cc ( p <.01, paired t-test) and 197.7 cc vs. 160 cc ( p =.02, paired t- test), respectively. The mean missed target volume was 4.3 cc. The percentage of off-target fractions and SD of rectal volumes in cITV-5, cITV-10, cITV-15, and cITV-20 were correlated. No other factors were correlated with the percentage of off-target fractions.

Conclusion An individualized approach can cover the target volume using a smaller PTV without increasing the overlapping bowel bag volume. We recommend an ITV margin of 10 mm for this individual approach. PO-1130 High-Dose-Rate Brachytherapy for primary vaginal melanoma treatment: a case report B. Pappalardi 1 , C.T. Delle Curti 2 , F. Piccolo 1 , C. Tenconi 3 , T. Giandini 3 , M. Carrara 3 , A. Cerrotta 1 1 Fondazione IRCCS Istituto Nazionale dei Tumori, Radiotherapy 2, Milan, Italy ; 2 University Milano-Bicocca, Radiotherapy, Milan, Italy ; 3 Fondazione IRCCS Istituto Nazionale dei Tumori, Medical physics, Milan, Italy Purpose or Objective Malignant melanoma of the vagina is a rare, aggressive malignancy with poor prognosis. The incidence is higher in post-menopausal women, ranging between 2.08/100,000 for 60- to 69-year-old women and 4.43/100,000 for 80- to 89-year-old women. We present a clinical case report of primary malignant vaginal melanoma in a 90 years old woman successfully treated with High-Dose-Rate Brachytherapy (HDR-BT). Material and Methods A 90-year-old woman referred post-menopausal vaginal bleeding. On gynecological examination, two raised lesions, were seen on the right third-inferior of vaginal wall, each one easily bleeding on contact; melanosis of right vaginal fornix was also observed. The lesions were biopsied and diagnosed as vaginal melanoma with a maximum tumor thickness of 3 mm. Staging by PET/CT did not show lymphadenopathy nor distant metastases. Considering the age and the anaesthesiological risk, patient was not suitable for surgery and has been candidate for HDR-BT. A vaginal multichannel applicator was used and treatment planning was performed on CT images acquired for each treatment fraction. The prescription dose was 25 Gy in 5 fractions to whole vagina, followed by a boost of 10 Gy in 2 fractions to the third- inferior of vaginal wall. The treatment was delivered at our Institution with an HDR remote after loading device provided with an Iridium-192 source. Results Patient completed the treatment with no interruptions. After the second treatment fraction (10 Gy) we clinically observed a dimensional reduction of the two lesions. After five fractions there was no bleeding. At the end of treatment, G1 vaginal sub-stenosis and dysuria were the main adverse effects. 18 months after the end of treatment, the patient has a local absence of disease. Conclusion The current treatment approach for primary vaginal melanoma includes wide local excision (WLE), radical surgery, chemotherapy and immunotherapy, alone or in