S2805
RTT - RTT contouring, target definition, and treatment planning
ESTRO 2026
Results: The study included 55 patients, with a mean age of 57 years. All were treated with 3D-CRT,with a total dose of 50.4Gy combined with capecitabine chemotherapy. The mean dose received by the BM was 22.3Gy, and the dosimetric constraint (Dmean<32Gy) was met in 65% of patients (n=36). Regarding hematological toxicities: Leukopenia was observed in 32.7% of patients (n=18), including 23.6% grade 1–2 (n =13) and 9.1% grade ≥ 3 (n =5). Grade 1 anemia was noted in 34.5% of cases (n =19), and grade ≥ 2 in 16.4% of cases (n =9). Grade ≥ 2 thrombocytopenia affected 5.5% of patients (n=3). No radiotherapy treatment delays were necessary due to hematological toxicity. After univariate analysis, a significant correlation was found between the mean dose to the BM and overall hematological toxicity (p<0.001), as well as with grade ≥ 2 toxicities (p <0.001). A significant correlation was also noted between BM dose and leukopenia (p <0.05), anemia (p <0.01), and thrombocytopenia (p <0.01). Multivariate analysis and linear regression showed that Dmean>32Gy received by the bone marrow (n =19) was associated with a significantly higher risk of toxicities: leukopenia (p<0.05), thrombocytopenia (p<0.001), anemia (p<0.01). Conclusion: This study demonstrates a significant correlation between BM dose and hematological toxicity. Rigorous BM delineation and adherence to Dmean ≤ 32Gy should be systematically integrated into rectal cancer radiotherapy planning. IMRT techniques offer optimal BM sparing while maintaining target coverage. Keywords: bone marrow, toxicity , rectal cancer Digital Poster 5056 Elderly Cervical Cancer patients: Dosimetric Aspects and Clinical Outcomes Irene Ávila Gómez, Beatriz Gil Haro, Arancha Gallego Barranco, Cristina de la Fuente Alonso, Marta López Valcárcer, Mariana Fernández-Vega Cerceda, Francisco José González Rodríguez, Raquel Benlloch Rodríguez, María Hernández Miguel, Irma Zapata Paz, Joaquín Velasco Jiménez, María Isabel García Berrocal, Peppa Abelairas Ramos, Clara Caballero Valls, Susana Sánchez Rico, José Cantillana Barrenas, Sofia Santana Jiménez, Jesús Romero Fernández, Sofía Córdoba Largo Radiation Oncology, Puerta de Hierro University Hospital, Madrid, Spain Purpose/Objective: To evaluate clinical outcomes, treatment-related morbidity, and dose-response factors predicting rectal and urinary side-effects in elderly patients with locally
advanced cervical cancer (LACC) treated with concurrent chemoradiation (CRT) and image-guided brachytherapy (IGBT). Material/Methods: Between January 2020 and December 2024, 92 patients (p) with stage IB–IV cervical carcinoma were treated with CRT and 3D IGBT following GEC-ESTRO recommendations. Twenty-one were aged >65 years (mean 74y, range 66–87). Tumour stages were IB (n=2), II (n=7), III (n=11), and IV (n=1). Patient characteristics are summarized in Figure 1.
Tumour involvement across eight anatomical regions (cervix, parametria, vagina, bladder, ureter, rectum, uterine body) was scored 0–3, generating T-score. Equieffective doses (EQD2) were calculated using the linear–quadratic model. Side effects were graded per CTCAE v5.0. Statistics: Kaplan-Meier method, log-rank test and chi square Results: After a median follow-up of 24 months (range 10–54), two-year overall survival (OS), local relapse-free survival (LRFS), and nodal relapse-free survival (NRFS) were 83.8%, 95%, and 95%, respectively. Two-year metastatic disease-free survival (MDFS) was 85%. Median High Risk Clinical Target Volume (HR-CTV) was 28.9 cc (16-111.6); median D90-HRCTV and D90-IRCTV were 90 Gy and 71.4 Gy. Median T-score was 5.Combined intracavitary/interstitial brachytherapy was performed in 16p (median six needles). T-score >4 correlated with interstitial use in 90% of cases (vs 50% when ≤ 4; p=0.08). No associations were found between HR-CTV > 30cc, T-Score and survival outcomes, though T-score >4 trended toward lower 2-
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