ESTRO 2024 - Abstract Book

S1229

Clinical - Head & neck

ESTRO 2024

For patients with midline extension of the primary tumor, there was a higher involvement of contralateral LNLs compared to patients without midline extension of the primary tumor (hypopharynx: Level II 30% (5%), Level III 27% (3%), Level IV 11% (0%), Level V 4% (0%); larynx: Level II 9% (0%), Level III 8% (0%)). Proven involvement of upstream LNLs increased the probability of involvement of downstream levels. For example in patients with hypopharynx-SCC, involvement of ipsilateral level III was 70% for patients with involvement of level II, compared to 24% for patients with healthy level II. For larynx-SCC patients, involvement of level II increased the risk of ipsilateral level III involvement from 4% to 74%. On the other hand, if level III proved to have no lymph node metastases, the risk of LNL involvement in level IV decreased from 21% - in case it was unknown if level III was involved - to 10% in hypopharynx-SCC patients, and from 3% to 0% in larynx-SCC patients. Figure 2 shows an example of how the data may lead towards personalization of the CTV-N in hypopharynx-SCC patients. The figure shows the frequency of lymph node metastases in ipsilateral level IV in hypopharynx-SCC, depending on T-stage and the involvement of adjacent LNLs. For example, if a patient is diagnosed with late T-stage hypopharynx-SCC with lymph node metastases in level III, the risk of ipsilateral level IV involvement is 36% (15 out of 42 patients). If a patient presents with early T-stage hypopharynx-SCC and there is no LNL involvement in level III, the frequency of metastases in level IV is only 7% (2 out of 28 patients).