ESTRO 2025 - Abstract Book

S1241

Clinical – Lower GI

ESTRO 2025

reduced posterior, lateral, and inferior margins to spare adjacent organs. This study evaluates the anatomical distribution and coverage of inguinal lymph nodes using these guidelines.

Material/Methods: We retrospectively analyzed data from patients with anal canal cancer and inguinal lymph node involvement treated with radiation therapy. Patient characteristics, including sex, BMI, weight, and skin infiltration by the primary tumor, were recorded. The anatomical localization of lymph nodes was mapped using clock-face quadrants relative to femoral vessels. Lymph node coverage was assessed according to the contouring guidelines proposed by Garda et al. Results: A total of 46 patients with malignancy-positive inguinal lymph nodes were analyzed. The cohort included 11 males and 35 females, with a mean weight of 66 kg (range 45–104 kg) and a median BMI of 22.1 (range 18.37–33.6); 40 patients had a normal BMI (18.5–24.9), and 6 were overweight or obese (BMI ≥ 30). Skin infiltration by the primary tumor was observed in 6 patients. Lymph node laterality distribution was 23 bilateral, 8 left-sided, and 10 right sided. Most patients (N = 34) presented with multiple lymph nodes, while 12 had a single node. Lymph nodes were located anterior (N = 18), medial (N = 12), lateral (N = 7), and posterior (N = 9) to the femoral vessels. Clock-face mapping showed the highest prevalence in the 12–3 o’clock quadrant (N = 24), followed by 12–4 (N = 7) and 11–3 (N = 5). No nodes were found between the 5 and 9 o’clock positions. Of the 73 CTVs delineated, 6 lymph nodes (8.2%) were located outside the proposed inferior margin, and 15 nodes (from 8 patients, 20.5%) were outside the superior margin. Conclusion: Preliminary findings suggest that while the proposed guidelines adequately cover most inguinal lymph nodes. Further validation is required to confirm their clinical applicability and optimize treatment planning. Results will be presented at the congress, underscoring the potential of these guidelines to enhance radiotherapy outcomes for anal canal cancer.

Keywords: Anal Cancer, inguinal lymph nodes, contouring

References: Garda AE, Navin PJ, Merrell KW, Martenson JA, Neben Wittich MA, Haddock MG, Sio TT, Rule WG, Ashman JB, Sheedy SP, Hallemeier CL. Patterns of inguinal lymph node metastases in anal canal cancer and recommendations for elective clinical target volume (CTV) delineation. Radiother Oncol. 2020 Aug;149:128-133. doi: 10.1016/j.radonc.2020.05.018. Epub 2020 May 15. PMID: 32417349.

3465

Digital Poster Total neoadjuvant treatment(TNT) followed by surgery in locally advanced rectal cancer: Three year’s experience of Bangladeshi tertiary level hospital Nowshin Taslima Hossain 1 , Masudul Hasan Arup 1,2 , Aditi Paul Chowdhury 1 , Jannatul Ferdause Rifat 1 , Rubama Karim 1 1 Radiation Oncology, AMCGH, Dhaka, Bangladesh. 2 Radiation Oncology, NICRH, Dhaka, Bangladesh Purpose/Objective: Despite the 3 rd most commonly diagnosed cancer around the world, till now we have to explore the best suitable treatment option for locally advanced rectal cancer (LARC). At present, neoadjuvant concurrent chemo-radiotherapy (CCRT) followed by chemotherapy and surgery are the most commonly practiced protocol in LARC. Our study aims to investigate the outcome of long course CCRT followed by chemotherapy that is Total Neoadjuvant Treatment (TNT) followed by surgery in LARC patients at three years after completion of treatment.