Locally advanced pyriform sinus carcinoma with a fixed neck node
A 58-year-old man presents with a 3-month history of progressive dysphagia, hoarseness and a 5 cm firm left level III node fixed to the underlying structures. Endoscopy shows a tumour involving the left pyriform sinus extending to the ipsilateral aryepiglottic fold and vocal cord, with reduced cord mobility. Imaging shows the tumour abutting the left thyroid cartilage lamina and extending 2 cm into the soft tissues of the neck, with no radiological evidence of contralateral nodal disease. He is planned for definitive chemoradiotherapy. The treating team is debating target volume design, particularly whether the contralateral neck and retropharyngeal nodes require elective treatment, and how to define the inferior border given the laryngeal involvement.
1. Justify the elective nodal target volumes for this patient, naming the nodal levels you would include and the anatomical reasoning behind each.
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The primary is a left pyriform sinus tumour crossing the aryepiglottic fold with a bulky ipsilateral level III node. The ipsilateral neck is clearly involved at level III, so levels II–IV are treated as gross-plus-adjacent disease, and level Ib should be included because of the bulky level II/III disease and the risk of retrograde spread to the submandibular region. The contralateral neck is at meaningful risk (roughly 15–20%) with a T3–4 lateralised larynx/hypopharynx primary, so elective contralateral levels II–IV are reasonable, sparing level I unless there is midline soft tissue involvement.
Retropharyngeal nodes (level VII) sit medial to the carotid sheath between the pharyngobasilar fascia and the prevertebral muscles; they are at risk for hypopharyngeal primaries and should be covered from skull base to approximately the hyoid, tapering laterally to avoid the parotid. The inferior border should extend at least 2 cm below the lowest radiological extent, and because the tumour reaches the vocal cord and thyroid cartilage, the border should sit below the cricoid, typically at the level of the first tracheal ring, to cover paratracheal (level VI) nodes.
2. The node is fixed to the sternocleidomastoid and the carotid sheath. Explain the anatomical basis for this finding and its implications for target delineation and dose prescription.
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Fixity implies tumour breach of the nodal capsule into the surrounding fascia and invasion of the sternocleidomastoid muscle and/or carotid sheath. The carotid sheath is a condensation of pretracheal, prevertebral and investing fascia; once breached, tumour can track along the sheath superiorly toward the skull base and inferiorly into the mediastinum. This explains the need to extend the level II–IV volume superiorly to the skull base and to include the sheath itself in the high-dose volume.
For planning, a fixed node requires a generous margin (typically 1–1.5 cm) around the gross nodal mass, and the sternocleidomastoid and sheath should be included in the GTV-to-CTV expansion. The prescription should treat the gross node to 70 Gy in 35 fractions while respecting spinal cord tolerance, which often means using a simultaneous integrated boost with IMRT and accepting some parotid dose. If the node remains fixed after induction, salvage neck dissection should be considered, and the surgical approach must anticipate carotid involvement.
3. The patient develops stridor and a new left vocal cord palsy at week 3. What anatomical structure has likely been compromised, and how does this change your management?
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A new vocal cord palsy with stridor suggests progression through the thyroid cartilage or involvement of the recurrent laryngeal nerve in the tracheo-oesophageal groove, or tumour extending into the paraglottic space and cricothyroid joint. The recurrent laryngeal nerve runs in the tracheo-oesophageal groove, and the left nerve loops around the aortic arch, making it vulnerable to level VI/paratracheal disease. Progressive stridor also raises the possibility of airway compromise from oedema or tumour bulk.
The immediate priority is airway assessment; if the airway is threatened, tracheostomy may be required, which changes the radiation field because the stoma must be included if there is subglottic extension. Re-planning should extend the inferior border to include the tracheostomy site and paratracheal nodes, and consider whether the cord palsy represents progression requiring a boost or a change to a surgical approach. Multidisciplinary review with ENT and consideration of a PET scan to exclude distant disease is warranted.