Would you consider elective neck nodal irradiation for a large >5 cm head and neck extramedullary solitary plasmacytoma arising from the nasal cavity?

A plasmocytoma in the nasal cavity may bear a higher risk for nodal involvement if it involves Waldeyer's ring or nasopharynx.

Adding ENI to the neck will certainly increase the risk of toxicity and only lead to a modest benefit in terms of isolated regional recurrence.

I would thus not perform elective irradiation of the neck.

This is in line with the ILROG recommendation (Tsang et al., PMID 29976492).