Patterns of lymphatic spread in hypopharyngeal squamous cell carcinoma - Findings from a multicenter study

Aiming for personalization of the elective nodal irradiation (ENI) in hypopharyngeal squamous cell carcinoma (SCC) patients, we describe the regional lymphatic spread patterns and risk of lymph node metastases, considering not only T-stage, location and lateralization of the primary tumor, but also involvement of adjacent lymph node levels (LNLs).

Patients with newly diagnosed hypopharyngeal SCC diagnosed at University Hospital Zurich between 2013-2021, UMCG Groningen between 2006-2023 and University Medical Center Freiburg between 2011-2019 were analyzed. Lymphatic involvement per level was assessed based on imaging and, if available, pathology. The dataset is made publicly available and can be visualized on https://lyprox.org/.

390 patients with hypopharyngeal SCC were included, 81 % had one or more cervical lymph node metastases. Overall prevalence of involvement in LNLs II, III, IV, V was consistent with literature: ipsilateral 65 %, 54 %, 23 %, 11 %; contralateral 25 %, 16 %, 6 %, 3 %. For lateralized tumors not affecting the midline (N = 143), contralateral involvement was 11 %, 4 %, 1 % 1 %. When contralateral LNL II was negative (N = 291), involvement of downstream LNLs III, IV, V was 5 %, 3 %, 1 %. Ipsilateral LNL IV involvement was reduced to 7 % in patients with negative LNL II and III.Ipsilateral level I and VII involvement was 6 % and 13 % in T4-tumors, but only 2 % and 3 % in T1-T3 tumors.

We provide detailed information about lymphatic spread patterns of hypopharyngeal SCC, where subgroups of patients may be identified in whom the ENI may be reduced. For lateralized tumors, contralateral irradiation may be limited to LNL II in patients without contralateral involvement.