High Risk Lymphatics By Head and Neck Sites

Based on the Revised Head and Neck Atlas of 2013 (Grégoire et al)

High Risk Head and Neck Nodal Basins

Nasopharynx

Level Ib — Submandibular Nodes
- May drop bilateral Ib nodes if N0 (node negative)
- May drop contralateral Ib nodes if contralateral Levels Ib/II are negative.
Level II — Upper Jugular Nodes (bilateral)
Level III — Middle Jugular Nodes (bilateral)
Level IVa — Lower Jugular Nodes (bilateral)
Level IVb — Medial Supraclavicular Nodes (bilateral)
Level Va/b — posterior triangle nodes (bilateral)
Level Vc — posterior triangle nodes(bilateral)
Level VIIa — Retropharyngeal Nodes (bilateral)
Level VIIb — Retro-styloid Nodes (bilateral)

Oropharynx

The general nodal basins in the drainage paths at risk for metastases include the following Nodal Groups:

Base of Tongue

The primary target volume is the base of tongue, with a generous anterior margin, epiglottis, superior pre-epiglottic space, lateral oropharyngeal walls, and bilateral neck nodes.

Level Ib — Submandibular NodesIPSILATERAL, if Level II nodes are positive.
Level II — Upper Jugular Nodes
Level III — Middle Jugular Nodes
Level IVa — Lower Jugular Nodes
Level IVb — Medial Supraclavicular Nodes
Level VII — Prevertebral: Retropharyngeal Nodes

In the N0 neck, all node levels are elective doses (CTV_ED). In the presence of node positive disease, the CTV_ID covers the adacent nodal compartments. These are generally dosed at 70 Gy, 63 Gy and 57 Gy respectively. 54 Gy at 1.64 Gy/fraction is also reasonable.

Posterior Oropharyngeal Wall

Since there can be extensive submucosal spread, the general target volume encompasses the primary with a 2 to 3 cm margin.

Soft Palate

Level II — Upper Jugular Nodes (bilateral)
Level III — Middle Jugular Nodes (bilateral)
Level IVa — Lower Jugular Nodes (bilateral)
Level IVb — Medial Supraclavicular Nodes (bilateral)
Level VII — Prevertebral: Retropharyngeal Nodes (bilateral)
Level Ib — Submandibular Nodes (ipsilateral Ib if Level II positive)

The target volumes include the ipsilateral tonsillar pillars, parapharyngeal space and lateral aspect of the Pterygoid muscle.

Tonsillar Fossa

For well lateralized T1 and T2 with limited or no extension to soft palate, N0-N1 disease, the contralateral nodes may be spared. If there is involvement with bilateral nodal drainage, such as soft palate, base of tongue, then the bilateral Level II to IV should be covered as well as the ipsilateral Level Ib nodes. In the case of locally advanced disease, the CTV-HD should also cover the tonsillar fossa, faucial pillars, soft palate, base of tongue, medial pterygoid muscle, and bilateral neck nodes. Arytenoids, larynx and esophageal inlet should be identified as organs at risk.

Hypopharynx

Pyriform Sinus

Radiotherapy is preferred for Stage I/II disease (T1-T2, N0-N1). Radiotherapy with concurrent chemotherapy is preferred for bulky disease (T2-T3). Neck dissection for tumors residual at 10 weeks post-treatment. For T4 disease (essentially outside of the pharynx, eg. invasion of cartilage, hyoid, soft tissues of the neck, encases carotid artery, extension to mediastinum), surgery is preferred.

IMRT CTV_HD-Pconsists of the GTV_p + ≥ 1 cm margin, covering the majority of the larynx due to superior-inferior mobility of the larynx. CTV_ID covers the neck compartments outside the CTV_HD + 2 cm cranial-caudal margin. CTV_ED include Levels II-V and the ipsilateral Level Ib.

For IMRT concomitant boost, the doses require 2 separate plans. The first plan delivers 54 Gy in 30 fractions to all CTVs at 1.8 Gy/fraction. The second (concomitant boost) plan adds 18 Gy in 10-12 fractions to CTV_HD as a second daily fraction at 1.8 Gy/fraction to 1.5 Gy/fraction.

Alternatively, SIB IMRT planning can be used. CTV_HD receives 70 Gy, CTV_ID receives 60-63 Gy, and CTV_ED receives 56-57 Gy in 30 fractions at 6 fractions/week.

If chemotherapy is used, treat at 2 Gy/fraction in 35 fractions.

Postoperative doses are 60 Gy to the pre-operative tumor bed (CTV_HD). If there are high risk factors, 66 Gy is used (positive margin, ECE, etc). The CTV_ID is the operative bed and is treated to a lower dose, while CTV_ED is treated to the same elective dose, usually 54 Gy.

Posterior Hypopharyngeal Wall

Doses are similar to pyriform sinus lesions. In the post-operative setting, the pre-vertebral space should be covered including 3 to 5 mm of the anterior vertebral bodies, even without demonstrable bone invasion.

Larynx

Supraglottic Larynx

Level II — Upper Jugular Nodes
- For T1/T2 N0, only Level II subdigastric nodes need to be covered.
- For T1/T2 N1, cover posterior Level Ib nodes
Level III — Middle Jugular Nodes
Level IVa — Lower Jugular Nodes
Level IVb — Medial Supraclavicular Nodes
Level Va/b — Posterior Triangle Nodes (upper/lower)
Level Vc — Lateral Supraclavicular Nodes

The typical SGL larynx volumes are CTV_HD-P which covers the GTV + ≥ 1 cm margin, particularly in the sup-inf plane. The larynx is highly mobile during swallowing functions. Previously with fluoroscopic methods, an idea of the excursion could be determined, but with CT methods, this is much more difficult to predict. The CTV_HD-N can be covered with a 1 cm expansion. The CTV_ID should encompass the CTV_HDwith a 2 cm superior-inferior margin. All others are CTV_ED and can be covered with the proposed elective neck dose, usually 54 - 57 Gy.

MDACC uses concomitant boost for T2 lesions treated with IMRT. The first plan treats the CTV_HD and the CTV_ID to 57 Gy in 30 fractions (1.9 Gy/fraction), and the CTV_ED to 54 Gy (1.8 Gy). A second IMRT plan is generated for BID concomitant boost to deliver 18 Gy in 10 fractions at 1.8 Gy/fraction in an afternoon dose.

Alternatively, a single plan simultaneous integrated boost plan can be developed with 70 Gy to CTV_HD , 60-63 Gy to the CTV_ID, and 57 Gy to the CTV_ED.

Glottic Larynx

For T1/T2 lesions, no nodal basins are treated due to the low risk of nodal involvement. The suprahyoid epiglottis is spared and the glottic larynx is covered.