Advertisement

Target Delineation of the Neck in Head and Neck Carcinomas

  • Joanne Zhung
  • Eli Scher
  • Nancy Lee
  • Ruben Cabanillas
Chapter
Part of the Medical Radiology book series (MEDRAD)

Abstract

IMRT is utilized for treatment in head and neck sites to maximize target coverage and decrease normal tissue toxicity, such as xerostomia and dysphagia. The most common at-risk nodal levels for head and neck cancers typically include levels I to VII and the lateral retropharyngeal lymph nodes (RPLN).

Keywords

Parotid Gland Oral Tongue Normal Tissue Toxicity Target Volume Delineation Oral Cavity Tumor 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

1 Anatomy and Patterns of Spread

IMRT is utilized for treatment in head and neck sites to maximize target coverage and decrease normal tissue toxicity, such as xerostomia and dysphagia. The most common at-risk nodal levels for head and neck cancers typically include levels I to VII and the lateral retropharyngeal lymph nodes (RPLN).

Ipsilateral neck treatment is reasonable for the clinically N0 neck in small T1–2 oropharyngeal carcinomas that are well lateralized (>1 cm between midline and medial extent of tumor), without significant soft palate or base of tongue involvement, as well as small carcinomas of the parotid gland, buccal mucosa, retromolar trigone, gingiva, or lateral border of the oral tongue (O’Sullivan et al. 2001). Early stage, small glottic larynx carcinomas (T1–2) do not require additional prophylactic neck treatment.

Typically, one ipsilateral nodal region beyond the pathologically involved level must be covered. Often, the N + neck requires coverage of levels IB to V, as well as coverage of the RPLN.

Lateral RPLN should be electively covered in clinically N0 pharyngeal tumors (naso-, oro-, and hypopharynx), supraglottic carcinomas, and high-risk paranasal carcinomas. The medial RPLN are not contoured in this chapter given low locoregional rates of relapse and the ability to spare pharyngeal constrictors (Feng et al. 2010). However, with posterior pharyngeal wall or gross RPLN involvement, it is recommended to include the medial and lateral RPLN. In the N0 neck, it is possible to start the superior extent of the RPLN at the inferior level of C1 and stop caudally at the superior edge of the hyoid bone. In the N + neck, especially in the presence of high level II adenopathy, RPLN should be treated up to the skull base. Routine inclusion of uninvolved RPLN will increase the dose to the pharyngeal constrictors and therefore should be carefully considered.

High level II and the retrostyloid (RS) lymph nodes (a cranial continuation of level II up to the skull base) can be spared in the N0 neck in order to reduce parotid gland dose. The N0 level II contours may begin where the posterior belly of the digastric muscle crosses the internal jugular vein (usually at the level of C1). In the N + neck, level II and the RS nodes should be treated up to the skull base (Figs. 2 and 3). The primary sites at highest risk of RS involvement include the nasopharynx and bulky involvement of upper level II due to retrograde flow.

Level I is at high risk for nodal involvement in oral cavity tumors. Specifically, IA drains the anterior oral cavity including the lip, the anterior mandibular alveolar ridge, the anterior oral tongue, and the floor of the mouth. Level IB is at highest risk in oral cavity tumors, the anterior nasal cavity, and cheek.

Levels II, III, and IV will be the most commonly treated nodal levels in the vast majority of mucosal head and neck cancers, given drainage patterns following the internal carotid artery and internal jugular vein. Levels II and III are at risk in nasopharynx, oropharynx, hypopharynx, and laryngeal tumors. Level IV is at risk of involvement in hypopharynx, larynx, and thyroid tumors.

Level V is infrequently involved in oral cavity, oropharyngeal, hypopharyngeal, and laryngeal tumors in the N0 neck. Posterior level V (Vb) has to be carefully included in thyroid, nasopharyngeal, parotid gland, and cutaneous carcinomas.

Level VI should be treated in laryngeal carcinomas with subglottic extension and in thyroid tumors.

Level VII should be treated in thyroid tumors, extending inferiorly for node-positive disease from the brachiocephalic vein to the carina.

Supraclavicular (SCV) nodes include part of the historically referenced “triangle of Ho.” Nasopharyngeal tumors are highest risk of metastases to the SCV region, bilaterally.

Surgical dissection of the neck may be performed prior to radiation treatment, depending on the location and treatment of the primary tumor (Table 1). All surgical clips should be covered in the clinical target volume, and microscopically positive mar-gins or ECE should be included in the high-risk tumor vol-ume.
Table 1

Types of neck dissection

Surgical neck management

Definition

Radical neck dissection

En bloc removal of neck levels I–V, sternocleidomastoid, internal jugular vein, spinal accessory nerve (CN XI)

Modified radical neck dissection

Removal of neck levels I–V but sparing of at least one uninvolved non-lymphatic structure (sternocleidomastoid, internal jugular vein, and/or accessory nerve)

Selective neck dissection

Removal of neck levels I–V, with preservation of at least one nodal level

Types

 

Supraomohyoid

Typically performed in oral cavity carcinomas, levels I–III, or in occasional skip metastases, to level IV (referred to as extended supraomohyoid neck dissection)

Lateral

Typically performed in oropharyngeal, hypopharyngeal, and laryngeal carcinomas: levels II–IV

Anterior compartment

Thyroid carcinomas at highest risk: level VI

Selected procedures from 2001 American Head and Neck Society

Well-lateralized N + tumors after unilateral neck dissection strongly warrant bilateral postoperative radiation therapy, due to altered lymphatic drainage.

Factors strongly recommended for postoperative chemoradiation, per EORTC 22931 and RTOG 9501, are extracapsular extension and positive margins.

2 Diagnostic Workup Relevant for Target Volume Delineation

Clinical examination, CT with IV contrast, and PET scan are the best modalities for the majority of cases. PET scan is helpful for small FDG-avid nodes that fall under size criteria on CT scan. Note the PET fusion may be misleading due to patient movement and should be evaluated closely for any inconsistencies without CT correlate. Ultrasound can be helpful when combined with fine-needle aspiration for staging the neck when other radiographic modalities are nondiagnostic.

MRI with contrast may be helpful in those who cannot receive CT with IV contrast and in cases where nodal adenopathy is obscured or is not easily delineated with contrast CT.

3 Simulation and Daily Localization

CT simulation with 3 mm slice thickness and IV contrast is preferred to ease delineation of vascular structures from lymph nodes. Supine patient positioning with rigid head cradle with the neck extended to reduce oral cavity exit dose is recommended. A custom thermoplastic mask to immobilize the nose, chin, and forehead is utilized. Shoulder pulls or other reproducible devices are used to reduce beam interference and allow adequate neck exposure. The CT simulation scan should encompass adequate superior extent of coverage of the primary disease and inferiorly to the level of the carina.

Image fusion depending upon the primary disease may include MRI and/or PET to aid in delineating involved gross disease in the neck. Attention should be paid to image fusion between primary disease and fusion to nodal disease, as patients will not have PET images in the CT simulation position (neck extended, shoulders pulled down).

Mediastinal windows should be used for contouring the neck nodal contents.

IGRT is recommended to aid in decreasing the PTV margins, depending upon patient positioning reproducibility and treatment machine considerations.

Uninvolved glottic larynx may be spared to limit RT-related speech disorders. Two possible techniques to treat the entire neck include an extended field IMRT or split field using an upper IMRT field matched to a lower anterior neck field (Fig. 1). Advantages of a split field include significantly reduced mean dose to the uninvolved larynx and inferior pharyngeal constrictors (Caudell et al. 2010). This technique is not recommended in laryngeal, hypopharyngeal, or unknown primary head and neck cases or when gross primary or nodal disease is present at the matchline or inferior to the larynx. In these cases, extended field IMRT will provide excellent coverage, whereas a split field may contribute to matchline failures or underdosage (Lee et al. 2007).
Fig. 1

Beam’s eye view of low anterior neck field

4 Target Volume Delineation and Treatment Planning

Fractionation schemes may vary between dose-painting IMRT and conventional IMRT (Table 2.) Suggested target volumes for nodal GTV and CTVs are detailed in Tables 3, 4, and 5.
Table 2

Selected IMRT dose fractionation schemes for the neck

 

Concomitant dose-painting IMRT

Postoperative dose-painting IMRT

Definitive dose-painting IMRT

 

Total dose/dose per fraction (Gy)

GTV

69.96/2.12, 66/2.0a

70/2.0c

69.96/2.12

70/2.0b

CTVhigh risk

59.4/1.8

66-60/2.2-2.0

59.4/1.8

59.5/1.7b

CTVlow risk

54/1.64

54/1.8 not surgically manipulated

56/1.7

56/1.70b

Optional CTV

CTVlow neck

50.4/1.8

  

aSmall, suspicious involved nodal disease

bSuggested dose levels without simultaneous integrated boost

cIf gross disease is present postoperatively

Table 3

Suggested target volumes for involved nodal disease

Target volumes

Definition and description

Concomitant or definitive dose-painting IMRT

GTV70

Neck nodes: clinically involved, nodes ≥ 1 cm, central necrosis, FDG-avid on PET, or biopsy proven. Include any suspicious or questionable nodes

GTV66

Small, involved nodal disease can be treated to 66 Gy

CTV70 or 66

No margin from GTV. Consider GTV70 or 66 + 5–10 mm margin if unclear or imaging quality is reduced

PTV70 or 66

CTV70 + 3–5 mm, variable

Postoperative IMRT

CTVpostop66

Extracapsular involvement. 70 Gy may be needed for residual gross disease

PTVpostop66

CTVpostop66 + 3–5 mm, variable

Table 4

Suggested target volumes for high-risk nodes

Target volumes

Definition and description

Concomitant or definitive dose-painting IMRT

CTV59.4

Typically, one level above and below grossly involved nodal disease. May involve entire involved muscle or at least one level above and below the muscle if ECE is present

PTV59.4

CTV59.4 + 3–5 mm, variable

Postoperative IMRT

CTVpostop60

Preoperative gross nodal disease with negative margins, entire operative bed without ECE. Include entire muscle (at least one level above and below the level of involvement) if involved. May include bilateral necks, depending on primary site

PTVpostop60

CTVpostop60 + 3–5 mm, variable

Table 5

Suggested volumes for low-risk nodes

Target volumes

Definition and description

Concomitant or definitive dose-painting IMRT

CTV54–56

Low-risk ipsilateral and/or contralateral neck

PTV54–56

CTV54–56 + 3–5 mm, variable

Postoperative IMRT

CTVpostop54

Contralateral neck and occasionally the uninvolved, low-risk, nonsurgically violated ipsilateral neck

PTVpostop54

CTVpostop54 + 3–5 mm, variable

5 Plan Assessment

The spinal cord is the only structure within the neck that carries the highest priority over tumor coverage. The brachial plexus (Hall et al. 2008), parotids and submandibular glands, mandible, temporomandibular joint, and constrictors are important normal tissue structures that need to be weighed appropriately when evaluating target coverage.

Occasionally, treatment of involved cranial nerves will warrant coverage to the base of the skull. In this case, the brainstem will therefore carry higher priority over tumor coverage.

Ideally, at least 95 % of the PTV should receive the prescription dose. The minimum dose to 99 % of the CTV should be >93 % of the dose. The maximum dose to the PTV should not exceed 115 %.

Several critical normal structures at risk in the neck should be carefully outlined to calculate dose. The spinal cord should be contoured at the top of vertebral body C1 down to T4 or 2 cm beyond the lowest extent of the target volume. The uninvolved pharyngeal constrictors should be contoured as suggested by Levendag et al. (2007). The glottic larynx should be contoured superiorly from the hyoid to the cricoid cartilage and including the arytenoids. Critical structures that traverse the length of the treated organ should be contoured 2 cm above and below the superior and inferior most extent of the combined target volumes. The structures at risk are detailed in Table 6.
Table 6

Intensity-modulated radiation therapy: normal tissue dose constraints

Target coverage

Constraints

PTVGTV

D95 ≥ prescription dose (70 Gy)

D05 ≤ 108 % of prescription dose

PTVCTV high risk

D95 ≥ prescription dose (59.4 Gy)

 

D05 ≤ GTV prescription dose

PTVCTV low risk

D95 ≥ prescription dose (54 Gy)

 

D05 ≤ CTVhigh risk prescription dose

Critical structures

Constraints

Spinal cord

Max < 45 Gy or 1 cc of the PRV cannot exceed 50 Gy

Brainstem

Max < 54 Gy or 1 % of PRV cannot exceed 60 Gy

Pharyngeal constrictors

V50 < 33 %, V60 < 15 % and mean <45 Gy

Brachial plexus

Max < 66 Gy, D05 < 60 Gy

Mandible and TMJ

Max < 70–66 Gy or 1 cc of the organ cannot exceed 75 Gy

Oral cavity

Mean < 40 Gy, mean <30 Gy if uninvolved

Parotid gland

(a) Mean ≤ 26 Gy in one gland

(b) Or at least 20 cc of the combined volume of both parotid glands will receive <20 Gy

(c) Or at least 50 % of one gland will receive <30 Gy

Submandibular gland

Mean < 39 Gy

Glottic larynx

Mean < 45 Gy or 20 Gy if uninvolved

Esophagus/postcricoid pharynx

Mean < 45–30 Gy

Based on guidelines used at Memorial Sloan Kettering Cancer Center and RTOG 1016. Dmax = 0.03 cc or 3 mm × 3 mm × 3 mm cube

A PRV or planning risk volume may be created for at-risk organs, such as the spinal cord (+5 mm) or brainstem (+3 mm).

6 Target Volumes for the Node-Negative and Node-Positive Neck

Fig. 2

Intact neck target delineation volumes. Patient with multiple level II and III nodal involvement with strongly suggestive extracapsular muscle involvement on CT. Each nodal level contoured with the left side showing examples of node-positive contours (right neck) and the right side showing examples of node-negative contours (left neck). LC longus capitis, PD posterior belly of the digastric muscle, AD anterior belly of the digastric muscle, GH geniohyoid muscle, ECA external carotid artery, ICA internal carotid artery, IJV internal jugular vein, CA common carotid artery, SCM sternocleidomastoid, SP superficial lobe of the parotid gland, DP deep lobe of the parotid gland, SG submandibular gland, BH body of hyoid, TZ trapezius muscle, LS levator scapulae muscle, SL splenius capitis muscle, CR cricoid cartilage, ASC anterior scalene muscles, BP brachial plexus, MSC middle scalene muscles, PSC posterior scalene muscles, BT brachiocephalic trunk, RBV right brachiocephalic vein, RSA right subclavian artery, LBV left brachiocephalic vein, LCA left common carotid artery, LSA left subclavian artery

Level

Superior/inferior

Medial/lateral

Anterior/posterior

Lateral RPLN

Base of the skull or inferior transverse process of C1 → cranial edge of the hyoid bone

Lateral edge of the longus capitis muscle → medial edge of internal carotid artery

Fascia under pharyngeal mucosa - > prevertebral muscles (longus colli, longus capitis)

RS

Jugular foramen → inferior aspect of C1 (top of level II)

Medial edge of internal carotid artery → deep parotid lobe

Parapharyngeal space → skull base and transverse process of C1

IA

Basilar edge of the mandible → body of the hyoid

Space between the anterior bellies of the digastric muscles

Platysma → geniohyoid muscles

IB

Superior aspect of the submandibular gland → body of the hyoid

Digastric muscle/ cranially the medial border of the mandible and caudally the platysma

Platysma → posterior submandibular gland

II

Inferior border of transverse process of C1 (continuation of the RS nodes) → inferior body of the hyoid bone

Medial internal carotid artery, paraspinal muscles → SCM

Anterior edge of internal carotid artery/SG → posterior edge of the SCM

II (low risk)

Posterior belly of the digastric muscle crosses the internal jugular vein

Same

Same

III

Caudal edge of the hyoid bone → inferior cricoid

Medial internal carotid artery and scalenus muscles → SCM

Anterior edge of SCM → posterior edge of SCM

IV

Caudal edge of the cricoid cartilage → 2 cm superior to the sternoclavicular joint

Thyroid gland, internal carotid artery and scalenus muscles → SCM

Anterior edge of SCM → posterior edge of SCM

Va

Cranial edge of the hyoid bone → CT slice containing the transverse cervical vessels

Paraspinal muscles → platysma and skin

Posterior border of the SCM → anterior edge of the trapezius muscle

Vb

Cranial edge of the cricoid → CT slice containing transverse cervical vessels

Same

Anterior edge of the trapezius muscle → posterior border of the trapezius muscle

VI

Caudal edge of the thyroid cartilage (hyoid bone in anterior floor of mouth, tip of the tongue or lower lip tumors) → manubrium

Trachea → medial edge of the SCM/thyroid gland

Platysma → thyroid cartilage/thyro-hyoid membrane/anterior border of the esophagus

SCV

Inferior border of IV/V → superior edge of the manubrium

Posterior edge of SCM/medial edge of carotids/medial clavicular edge → trapezius superiorly, medial edge of the clavicle inferiorly

SCM/clavicle → posterior edge of carotids/anterior surface of scalene muscles

Fig. 3

Postoperative nodal level delineation. Example of a patient undergoing a modified radical neck dissection, with sacrifice of the sternocleidomastoid, with extracapsular extension in level II and found to have involvement of the ipsilateral retrostyloid. Each nodal contour depicts involved node involved/positive side on the left (patient’s right) and uninvolved, node-negative side on the right (patient’s left)

Suggested Reading

Gregoire V et al (2003) CT-based delineation of lymph node levels and related CTVs in the node-negative neck: DAHANCA, EORTC, GORTEC, NCIC, RTOG consensus guidelines. Radiother Oncol 69(3):227–36.

Gregoire V et al (2006) Proposal for the delineation of the nodal CTV in the node-positive and the post-operative neck. Radiother Oncol 79(1):15–20.

Gregoire V et al (2013) Delineation of the neck node levels for head and neck tumors: A 2013 update, DAHANCA, EORTC, HKNPCSG, NCIC CTG, NCRI, RTOG, TROG consensus guidelines. Radiother Oncol. Epub ahead of print

Mourad WF et al (2013). Cranial nerves IX-XII contouring atlas for head and neck cancer. RTOG.org. Retrieved 5 Oct 2013 from http://www.rtog.org/LinkClick.aspx?fileticket=B7fuSx-B1GU%3D&tabid=229

Young B (2011) Neuroanatomy modules: skull base CT. Retrieved 13 Nov 2013 from http://headneckbrainspine.com/Skull-Base-CT.php

References

  1. Caudell JJ et al (2010) Comparison of methods to reduce dose to swallow-related structures in head and neck cancer. Int J Radiat Oncol Biol Phys 77(2):462–467CrossRefGoogle Scholar
  2. Feng FY et al (2010) Intensity-modulated chemoradiotherapy aiming to reduce dysphagia in patients with oropharyngeal cancer: clinical and functional results. J Clin Oncol 28(16):2732–2738CrossRefGoogle Scholar
  3. Hall WH et al (2008) Development and validation of a standardized method for contouring the brachial plexus: preliminary dosimetric analysis among patients treated with IMRT for head-and-neck cancer. Int J Radiat Oncol Biol Phys 72(5):1362–1367CrossRefGoogle Scholar
  4. Lee NY et al (2007) Choosing an intensity-modulated radiation therapy technique in the treatment of head-and-neck cancer. Int J Radiat Oncol Biol Phys 68(5):1299–1309CrossRefGoogle Scholar
  5. Levendag PC et al (2007) Dysphagia disorders in patients with cancer of the oropharynx are significantly affected by the radiation therapy dose to the superior and middle constrictor muscle: a dose-effect relationship. Radiother Oncol 85(1):64–73CrossRefGoogle Scholar
  6. O’Sullivan B et al (2001) The benefits and pitfalls of ipsilateral radiotherapy in carcinoma of the tonsillar region. Int J Radiat Oncol Biol Phys 51(2):332–343CrossRefGoogle Scholar

Copyright information

© Springer International Publishing Switzerland 2014

Authors and Affiliations

  • Joanne Zhung
    • 1
  • Eli Scher
    • 2
  • Nancy Lee
    • 2
  • Ruben Cabanillas
    • 3
  1. 1.Department of Radiation OncologyTufts Medical CenterNew YorkUSA
  2. 2.Department of Radiation OncologyMemorial Sloan-KetteringNew YorkUSA
  3. 3.Department of Radiation OncologyInstitute of Molecular and Oncological Medicine of Asturias (IMOMA)OviedoSpain

Personalised recommendations