ESTRO 2025 - Abstract Book

S1204

Clinical – Lower GI

ESTRO 2025

regardless of clinical stage [1,2]. However, neither of these regions is the first-echelon nodal station for anal primaries, and there is no conclusive evidence on the risk of microscopic involvement of these LNS in patients with cT1-2N0 disease. Thus, the recommendation of inclusion of these regions into elective clinical target volume (CTV) in early anal canal cancer is based on limited and unconvincing evidence [3,4]. Material/Methods: A systematic review and meta-analysis were performed to determine the rates of regional recurrence in the upper pelvic and external iliac LNS, without concomitant local recurrence or persistent primary tumour, in patients with early anal canal cancer (cT1-2N0) treated with radio(chemo)therapy without elective nodal irradiation (ENI) of these LNS. Results: The pooled weighted rate of regional recurrence in the upper pelvic LNS was 1.1% (95% confidence interval [CI]: 0.1– 2.1%) among 466 cT1-2N0 patients treated with radio(chemo)therapy not covering these LNS (Table, Figure). None of 223 patients treated with ENI not covering external iliac LNS had a recurrence in this region after radio(chemo)therapy. Table. Regional recurrence in the upper pelvic lymph nodes (above the caudal edge of the sacroiliac joints) and in the external iliac lymph nodes in cT1-2 anal canal cancer patients treated with radio(chemo)therapy with limited elective nodal irradiation (upper border of the CTV at the bottom of the sacroiliac joints)