ESTRO 2025 - Abstract Book

S970

Clinical – Head & neck

ESTRO 2025

involvement (without T1-glottic SCC patients) stratified by T-stage was visualized (Figure 1). For T2-glottic tumors (N=194), ipsilateral levels II, III, IV, V were involved in 3,6%, 1,6%, 0,5%, 0%, suggesting that elective LNL irradiation could potentially be omitted. Contralateral involvement occurred in only one case (LNL III). T3/T4-glottic tumors (N=236) showed higher LNL involvement rates than T2-glottic tumors (e.g. ipsilateral LNL II 17% vs 3,6%, LNL III 14% vs 1,6%, contralateral LNL II 7% vs 0%). For T3- and T4-glottic tumors without midline extension (N=37), there was no contralateral involvement, which suggests contralateral LNLs could potentially be omitted from the elective CTV (Figure 2). In T3/T4-glottic patients without ipsilateral LNL II involvement (N=220), involvement of ipsilateral LNLs III, IV, V was reduced to 2,7%, 1,8%, 0,5%, suggesting that elective irradiation may be limited to LNL II in cN0 patients. Patients with supraglottic SCC showed more LNL involvement: e.g. ipsilateral LNL II 46%, contralateral LNL II 21%. However, for patients with supraglottic SCC the contralateral elective CTV might potentially be reduced. In patients without contralateral LNL II involvement (N=265), involvement of downstream levels was rare (LNL III 4%, LNL IV 2%). Without midline extension of the primary tumor (N=75), contralateral LNL involvement was reduced to 2.7% for contralateral LNLs II, III, IV.