S678
Clinical – Lower GI
ESTRO 2026
Digital Poster 34 Chemoradiotherapy for anal cancer: a
monocentric retrospective analysis comparing dosimetry and outcome before and after guideline implementation Arnaut Defraine 1 , Katleen Verboven 2 , Pascal Peeters 3 , Elisabeth Stragier 3 , Bert Houben 4 , Christophe Severi 5 , Jaarke Vannoote 5 , Kim Govaerts 6 , Joep Knol 6 , Kurt Van der Speeten 6 , Jeroen Mebis 1,7 , Philippe P Bulens 2 1 Biomedical Sciences, Hasselt University, Hasselt, Belgium. 2 Radiation Oncology, Limburg Oncology Center, Hasselt, Belgium. 3 Gastroenterology, Jessa Hospital, Hasselt, Belgium. 4 Abdominal Surgery, Jessa Hospital, Hasselt, Belgium. 5 Gastroenterology, Hospital Oost-Limburg, Genk, Belgium. 6 Abdominal Surgery, Hospital Oost-Limburg, Genk, Belgium. 7 Medical Oncology, Limburg Oncology Center, Hasselt, Belgium Purpose/Objective: Squamous cell carcinoma of the anus (SCCA) is the most common type of anal cancer, with increasing incidence rates [1]. Chemoradiotherapy is the gold standard treatment, but radiotherapy dose (de- )escalation is being investigated [2]. This monocentric retrospective analysis focused on comparing dosimetry and oncological outcome before and after standardised guideline implementation with slight
Conclusion: After implementation of standardised guidelines, slight radiotherapy dose de-escalation maintained oncological outcomes and improved dosimetry outcomes which may potentially translate into limited toxicity. References: 1. Tchelebi LT, Eng C, Messick CA, Hong TS, Ludmir EB, Kachnic LA, Zaorsky NG. Current treatment and future directions in the management of anal cancer. CA Cancer J Clin. 2022;72(2):183-95 2. Eng C, Ciombor KK, Cho M, Dorth JA, Rajdev LN, Horowitz DP, et al. Anal Cancer: Emerging Standards in a Rare Disease. J Clin Oncol. 2022;40(24):2774-88. 3. Ng M, Leong T, Chander S, Chu J, Kneebone A, Carroll S, et al. Australasian Gastrointestinal Trials Group (AGITG) contouring atlas and planning guidelines for intensity-modulated radiotherapy in anal cancer. Int J Radiat Oncol Biol Phys. 2012;83(5):1455-62. 4. Radiologists TRCo. National guidance for volumetricmodulated arc therapy (VMAT) or intensity-modulated radiotherapy(IMRT) in anal cancer 2024 Keywords: anal cancer, dosimetry, guideline implementation
dose de-escalation. Material/Methods:
Patients treated with chemoradiotherapy for SCCA at the department of the Limburg Oncology Centre between January 1, 2015 and June 30, 2024 were included. Clinicopathological data and oncological outcome data were collected from patients’ electronic health records while radiotherapeutic dosimetry data was collected from Aria. Kaplan-Meier analysis was performed to compare oncological outcomes between a group treated before guideline implementation with dose to the primary tumour > 54 Gy, and a group after implementation with dose < 54 Gy [3,4]. Dosimetry comparison was performed using the Kolmogorov- Smirnov test. Results: 69 patients were included: 26 in the > 54 Gy group, and 43 in the < 54 Gy group. In general, oncological outcome was favourable. Similar oncological outcome (overall survival, local recurrence, permanent colostomy, distant recurrence, and nodal recurrence) was observed between both patient groups (p > 0.05) (Figure 1). In patients treated after standardised guideline implementation, radiation dose to organs at risk (OARs) was lower as compared to patients treated before implementation (p < 0.001) (Figure 2).
Mini-Oral 350
Early determination of tumor response to neoadjuvant chemotherapy alone without radiation for locally advanced rectal Cancer Yu Shen, Tianxiang Jiang, Ziqiang Wang Colorectal Cancer Center, West China Hospital, Sichuan University, Chengdu, China
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