ESTRO 2024 - Abstract Book

S1101

Clinical - Gynaecology

ESTRO 2024

Martina Midulla 1,2 , Andrei Fodor 1 , Miriam Torrisi 1,2 , Laura Giannini 1,2 , Roberta Tummineri 1 , Chiara L Deantoni 1 , Sara Broggi 3 , Lucia Perna 3 , Claudio Fiorino 3 , Stefano Arcangeli 2,4 , Nadia G Di Muzio 1,5 1 IRCCS San Raffaele scientific Institute, Department of Radiotherapy, Milan, Italy. 2 University of Milano-Bicocca, Department of Radiotherapy, Monza, Italy. 3 IRCCS San Raffaele scientific Institute, Department of Medical Physics, Milan, Italy. 4 IRCCS San Gerardo dei Tintori, Department of Radiotherapy, Monza, Italy. 5 Vita-Salute San Raffaele University, Department of Radiotherapy, Milan, Italy

Purpose/Objective:

Older studies analyzing lymph nodal (LN) relapse in gynecological tumors proposed extended nodal radiotherapy (ENRT) of the interested chain as salvage treatment [1]. Subsequently, a Simultaneous Integrated Boost (SIB) of the positive nodes was added [2]. In recent years stereotactic body radiotherapy (SBRT) has been proposed in several large multi-institutional studies, with promising results [3,4,5,]. There is, to date, no evidence as to which treatment is more effective for LN relapses. In this mono-institutional retrospective study we analyze the outcomes and toxicity of salvage ENRT with SIB versus SBRT for LN relapse in gynecological cancer patients (pts).

Material/Methods:

From February 2007 to April 2023, 58 gynecological cancer pts with LN relapse were treated with fluoro-deoxy glucose positron emission tomography/computed tomography (PET/CT) guided-salvage RT at our Institution: 23 pts received ENRT and Simultaneous Integrated Boost (SIB) to PET positive LN, and 35 pts SBRT to positive PET/TC LN. One hundred and seventy-five positive LN’s were treated. In the ENRT group, the SIB Planning Target Volume (PTV) of the LNs was defined by adding a 5 mm isometric margin to the PET/CT Gross Tumor Volume (GTV-PET). A median Biological Equivalent Dose (BED) of 76.5 Gy (Interquartile range, IQR 74.4; 78.8) was delivered. The LN chain PTV (pelvic, para-aortic or extra abdominal), was obtained by adding a 7 mm isometric margin to the clinical target volume (CTV, the LN chain). In the SBRT group, PTV was obtained by adding a 3 mm isometric margin to GTV-PET; a median BED of 72 Gy (IQR 59.6;76.5) was prescribed. The treatment was delivered with TomoTherapy® (Accuray, Madison, WI) or RapidArc® (Varian Medical Systems, Palo Alto, CA) for ENRT pts and with CyberKnife® (Accuray, Sunnyvale, CA) or TomoTherapy, for SBRT pts. Toxicity was assessed using CTCAE version 5 criteria. Median follow-up was 81.1 (IQR 48.5; 117.2) and 37.0(IQR 21.3; 58.4) months for ENRT and SBRT, respectively. Primary histology in the ENRT and SBRT groups were, respectively: ovarian in 52.2% vs 45.7% pts; endometrial in 39.1% vs 25.7% pts; cervix, vagina and vulva in 8.7% vs 28.6% pts. Local relapse was registered in 8.7% and 14.3% in ENRT and SBRT groups, respectively; regional relapse in 34.8% vs 34.3%, and distant relapse in 78.3% vs 57.1%. Overall Survival in the two groups was not statistically different (60.9% for ENRT and 65.7% for SBRT). Kaplan Meier estimates of overall survival and disease-free survival are presented in Figures 1 and 2. Maximum acute and late toxicity (genitourinary, gastrointestinal and other), based on treatment site, was grade (G) 2, except for one patient with acute G3 erythema, and one patient with late bone insufficiency fracture, both in the ENRT group. A significant association between treatment group and acute toxicity was observed, with higher grade toxicity in the ENRT group. Results: