Hypopharyngeal Carcinoma Target Delineation

Hypopharyngeal carcinoma target delineation starts with anatomy. The site extends from the top of the hyoid bone, around C4, to the bottom of the cricoid cartilage, around C6, and sits between the oropharynx, the larynx, and the cervical esophagus. Once a tumor develops there, speech and swallowing are immediately part of the planning equation because submucosal spread crosses planes that offer very little resistance.

Most patients also bring meaningful nodal risk to the table, so endoscopy, contrast-enhanced CT or MRI, PET/CT, careful simulation, and IMRT all need to be integrated from the start. For the broader framework, see the Target Volume Delineation and Field Setup – Complete Clinical Guide.

Anatomy and patterns of spread

The hypopharynx does not behave like a tidy compartment. It contains the paired pyriform sinuses, the posterior pharyngeal wall, and the post-cricoid region, yet tumors often move from one subsite to another, invade the larynx, and reach adjacent soft tissue because the anatomic barriers are minimal.

Pyriform sinus tumors account for 65% to 85% of hypopharyngeal cancers. The posterior pharyngeal wall contributes about 10%, and the post-cricoid region less than 5%. When disease reaches the arytenoids, aryepiglottic folds, or paraglottic space, the contouring discussion quickly overlaps with laryngeal anatomy, so it is useful to compare the findings with our dedicated larynx cancer delineation guide.

Patterns of spread by subsite

The table below condenses the spread pathways that matter most for contouring. It is the practical map for deciding what belongs in the high-risk CTV before dose is even assigned.

Hypopharyngeal subsite	Patterns of spread
Pyriform sinus	Anteromedial: arytenoids, aryepiglottic folds, intrinsic laryngeal muscles, with possible vocal cord fixation, and the paraglottic space. Posterior: constrictor muscles and prevertebral tissue. Lateral: paraglottic space, thyroid cartilage, and lateral neck. Superior: oropharynx, pre-epiglottic space, and the thyrohyoid membrane, with referred otalgia from the internal branch of the superior laryngeal nerve. Inferior: post-cricoid area. Lymph nodes: most often retropharyngeal, level II, and level III; additional risk includes level IV and level VI when inferior tumors involve the apex.
Posterior pharyngeal wall	Superior: extension to the oropharynx. Inferior: extension to the cervical esophagus. Posterior: prevertebral fascia and retropharyngeal space. Lymph nodes: retropharyngeal nodes and levels II through IV.
Post-cricoid region	Anterior: laryngeal invasion, with risk of vocal cord fixation. Superior: pyriform sinuses. Inferior: cricoid cartilage and cervical esophagus. Lymph nodes: levels II through IV and paratracheal nodes.

Source: Target Volume Delineation and Field Setup, 2nd Edition (Table 5.1)

Nodal behavior drives management here. The chapter emphasizes frequent involvement of bilateral cervical nodes and lateral retropharyngeal nodes, with posterior level V, level VI, and even superior mediastinal nodes entering the field for post-cricoid tumors and inferior pyriform sinus lesions that reach the apex. Even when the neck is clinically N0, 30% to 35% of patients harbor pathologic nodal disease. Level Ib is rarely involved, but in node-positive necks its incidence ranges from 5% to 20%.

Small anatomic details have real planning consequences. The pyriform sinus is a paired potential space lateral and posterior to the larynx, widest superiorly and narrowing toward the cricoarytenoid joint in an inverted-cone shape. The posterior hypopharyngeal wall is a continuation of the lateral and posterior pharyngeal wall and encloses the constrictor muscles. The post-cricoid region is the least common subsite, but skip spread to the cervical esophagus can occur.

Diagnostic workup relevant for target delineation

Most hypopharyngeal cancers are squamous cell carcinomas. Verrucous carcinoma, basaloid squamous carcinoma, spindle cell carcinoma, and minor salivary gland tumors form a smaller group, but the workup logic remains the same: focus the history on tobacco and alcohol exposure, otalgia suggesting vagal involvement, respiratory function, voice quality, and baseline swallowing, especially when organ preservation is under consideration.

The chapter also pushes for a hands-on examination. Palpate the base of tongue to assess pre-epiglottic extension, document laryngeal mobility, check for a thyroid click, and record cervical adenopathy. Flexible fiberoptic endoscopy is critical for identifying involvement of adjacent mucosal subsites and for detecting vocal cord fixation; phonation and Valsalva can improve visualization of the hypopharynx.

AJCC 8 staging for hypopharyngeal cancer

The staging system below organizes the features that most directly change treatment volume. In radiation planning it is not just prognostic. It tells you when cartilage, esophagus, prevertebral fascia, and bilateral nodal chains must move into the contour.

Stage	Criteria
T1	Tumor limited to one hypopharyngeal subsite. 2 cm or less in greatest dimension.
T2	Tumor invades more than one hypopharyngeal subsite or an adjacent site. Tumor measures 2 to 4 cm. No hemilarynx fixation.
T3	Tumor larger than 4 cm. Or fixation of the hemilarynx. Or extension to esophageal mucosa.
T4a	Invasion of the thyroid or cricoid cartilage, hyoid bone, thyroid gland, esophageal muscle, or central compartment soft tissue, including prelaryngeal strap muscles and subcutaneous fat.
T4b	Invasion of prevertebral fascia, encasement of the carotid artery, or involvement of mediastinal structures.
N0	No regional lymph node metastasis.
N1	Metastasis in a single ipsilateral lymph node. Up to 3 cm with ENE negative.
N2a	Metastasis in a single ipsilateral node 3 to 6 cm with ENE negative.
N2b	Metastases in multiple ipsilateral nodes, none larger than 6 cm, all ENE negative.
N2c	Metastases in bilateral or contralateral nodes, none larger than 6 cm, all ENE negative.
N3a	Metastasis in a lymph node larger than 6 cm with ENE negative.
N3b	Metastasis in any node with clinically overt ENE positive.

Source: Target Volume Delineation and Field Setup, 2nd Edition (Table 5.2)

Contrast-enhanced CT or MRI is then used to define pre-epiglottic or paraglottic extension, laryngeal spread, gross cartilage invasion, soft-tissue extension, esophageal invasion, and extracapsular spread. PET/CT helps refine borders that can be subtle, especially at the inferior apical extent of the primary, and it improves identification of hypermetabolic nodal disease.

Simulation and daily localization

Simulation should be simple and reproducible: supine position, head rest, neck hyperextended or supported with a shoulder pull board to move the shoulders out of beam entry, and custom immobilization with a thermoplastic mask. In postoperative cases, surgical scars should be wired.

The recommended planning scan uses 3 mm slices from the top of the skull to T5. Intravenous contrast is part of the standard protocol unless there is a medical contraindication, and the isocenter is typically placed at the arytenoids.

For daily localization, the preferred approach is daily cone beam CT aligned to the larynx. Daily kilovoltage imaging aligned to bony anatomy, combined with weekly cone beam CT, is still considered acceptable.

Target volume delineation and treatment planning

The chapter is clear: IMRT is the recommended technique for hypopharyngeal cancer. The main strategy uses an initial 30-fraction plan with dose painting, delivering 54 Gy in 1.8 Gy fractions to low-risk subclinical regions and 60 Gy in 2 Gy fractions to high-risk subclinical regions, followed by a 10 Gy cone down to gross disease for a total of 70 Gy in 35 fractions. A single dose-painted plan to 70 Gy in 33 to 35 fractions is also acceptable.

Another practical point should not be ignored: extended IMRT is preferred over the use of a low anterior neck field. High-risk regions, and sometimes gross disease, can easily sit inside the low-dose part of the match line.

Early-stage disease corresponds to T1N0 or T2N0 by AJCC 8 and represents a minority of presentations. Even then, definitive radiation is often favored because it aims for local control while preserving the larynx, speech, and swallowing. Given the high rate of occult nodal disease and the central position of the hypopharynx, bilateral nodal chains should still be included.

Advanced disease, defined here as T3 or greater or any node-positive presentation, can be managed with definitive chemoradiation, laryngectomy followed by adjuvant therapy, or induction chemotherapy followed by local therapy. Larynx-preservation strategies are not ideal for advanced T4 disease, poor baseline function, or patients unlikely to recover function, although carefully selected exceptions exist.

The case examples in the chapter reinforce a few recurring planning patterns: lateral retropharyngeal and retrostyloid regions often extend to the skull base; the larynx is included from the top of the hyoid to the bottom of the cricoid in the higher-risk subclinical volume; and inferior tumors, apex-involving pyriform sinus lesions, and post-cricoid primaries frequently push coverage into level IV, level VI, airway extending 2 cm below the cricoid, and in some cases the superior mediastinum. For a well-lateralized node-positive tumor, the ipsilateral neck may receive 60 Gy while the node-negative side receives 54 Gy.

Suggested volumes for gross disease

Before expanding subclinical volumes, the chapter defines the gross disease core in a compact way. This table organizes the 70 Gy GTV, CTV, and PTV for the primary and involved nodes.

Target volume	Definition and description
GTV_70	Primary: all gross disease seen on CT, MRI, or PET. Lymph nodes: nodes 1 cm or larger, or suspicious FDG-avid lymph nodes.
CTV_70	At MSKCC, an additional CTV_70 margin is not routinely used, but it can be added if disease extent is uncertain. Primary: GTV_70 + 5 mm. Lymph nodes: GTV_70 + 3 mm. In general, if no extra CTV margin is needed, GTV_70 and CTV_70 are the same.
PTV_70	Primary: CTV_70 + 3 to 5 mm, depending on comfort with daily imaging and setup uncertainty. Lymph nodes: CTV_70 + 3 to 5 mm.

Source: Target Volume Delineation and Field Setup, 2nd Edition (Table 5.3). The table note recommends 70 Gy in 2 Gy fractions; in the 70/60/54 approach, a simultaneous plan can deliver 60 Gy in 2 Gy fractions and 54 Gy in 1.8 Gy fractions before a single 10 Gy cone down to PTV_70.

Postoperative radiation is indicated for the adverse pathologic features listed in the chapter, based on NCCN v.2019: positive margins, close margins, extranodal extension, pT3 to pT4 primary disease, pN2 to pN3 nodal disease, and perineural, vascular, or lymphatic invasion. Adjuvant treatment should ideally begin within 6 weeks of surgery. The entire surgical bed and the dissected node-positive neck belong in the high-risk subclinical region, while the dissected node-negative neck can be treated as low risk.

Suggested volumes for the high-risk subclinical region

Table 5.4 is the practical center of the chapter. It shows how the primary volume expands by subsite and how nodal coverage changes in the presence of nodal disease, inferior extension, or midline involvement.

Target volume	Definition and description
CTV_60	Primary: GTV_70 with a 1 cm margin, plus the entire involved subsite and the larynx from hyoid to cricoid. Include adjacent mucosal and submucosal sites at risk of microscopic infiltration. Pyriform sinus: cover arytenoids, paraglottic space, and thyroid cartilage for laterally involved lesions; constrictor muscles or prevertebral muscle when there is posterior extension; pre-epiglottic space or oropharyngeal structures for superior extension; and the post-cricoid area for inferior lesions. Posterior pharyngeal wall: include prevertebral fascia and retropharyngeal space, consider adjacent oropharynx for superior extension, and consider proximal cervical esophagus for inferior extension. Post-cricoid region: consider covering the pyriform sinuses for superiorly extending lesions, cover the cricoid cartilage if involved, and include proximal cervical esophagus for inferior extension. Lymph nodes: every lymph node in CTV_70 remains included. Ipsilateral or node-positive neck: cover lateral retropharyngeal nodes starting at the skull base at the carotid canal entrance and cover levels II through IV, including the retrostyloid space for superior level II. For inferior hypopharyngeal tumors, pyriform sinus tumors involving the apex, and advanced T stage, include level VI. For midline post-cricoid and posterior pharyngeal wall tumors with nodal involvement, consider bilateral lateral retropharyngeal coverage, levels II through IV, and level VI. For inferior tumors, consider paratracheal coverage in the superior mediastinum. In a node-positive neck, keep retropharyngeal coverage. Consider ipsilateral level Ib if level II is involved. If level II through IV disease is posterior, consider level V. Postoperative cases should include the entire surgical bed and the bilateral dissected neck, together with clips and wired scars. Areas at risk for a positive margin or extracapsular spread should be contoured with the surgeon and may receive 66 Gy.
PTV_60	CTV_60 + 3 to 5 mm, depending on confidence in daily target localization.

Source: Target Volume Delineation and Field Setup, 2nd Edition (Table 5.4). The table recommends 60 Gy in 2 Gy fractions; in the 70/60/54 approach, treatment can be planned with 60 Gy in 2 Gy fractions and 54 Gy in 1.8 Gy fractions before a single 10 Gy cone down to PTV_70.

Suggested volumes for the low-risk subclinical region

When the contralateral neck is clinically negative or the case is N0, the chapter narrows coverage to a more selective elective volume. Even then, it keeps close attention on retropharyngeal nodes and midline disease.

Target volume	Definition and description
CTV_54	Contralateral or N0 neck: cover lateral retropharyngeal lymph nodes, which may start at the C1 vertebral body, and levels II through IV. Level II may start where the posterior belly of the digastric crosses the internal jugular vein. Exception: in a midline hypopharyngeal tumor, the bilateral retropharyngeal nodal region should be included. Second exception: if a midline tumor is node positive, the contralateral neck also becomes high risk.
PTV_54	CTV_54 + 3 to 5 mm, depending on confidence in daily target localization.

Source: Target Volume Delineation and Field Setup, 2nd Edition (Table 5.5). The table note preserves the 70/60/54 planning schema with 60 Gy in 2 Gy fractions, 54 Gy in 1.8 Gy fractions, and a single 10 Gy cone down to PTV_70.

After induction chemotherapy, planning should not rely on the post-treatment appearance alone. The chapter recommends fusing pre-chemotherapy imaging, incorporating the pre-treatment extent of gross disease into the high-risk subclinical volume, and then adapting that CTV to post-treatment anatomy while excluding air and bone.

Suggested reading

The reading list rounds out the clinical picture well. Biau and Gregoire updated the head and neck nodal target volume consensus for IMRT and VMAT in 2019. Gupta and colleagues analyzed 501 patients with hypopharyngeal carcinoma managed with a nonsurgical approach. The 10-year EORTC 24891 results showed that induction chemotherapy followed by radiotherapy preserved the larynx in more than half of survivors without compromising disease control or survival.

On the technical side, Lee and colleagues described the MSKCC experience with concurrent chemotherapy and IMRT for locoregionally advanced laryngeal and hypopharyngeal cancers. Prades and coauthors then reported a phase III trial in pyriform sinus carcinoma showing a survival advantage for concurrent chemoradiotherapy over induction chemotherapy followed by radiotherapy.