Radiation Oncology: A Question-Based Review

36
Neck Management and Postoperative Radiation Therapy for Head and Neck Cancers

Steven H. Lin and Vincent J. Lee

image Background


What is a radical neck dissection?

Radical neck dissection is a procedure that removes all LN levels (“comprehensive”) from levels I–V and other structures (the sternocleidomastoid, jugular vein, spinal accessory nerve, omohyoid, and submandibular gland).

What is a modified radical neck dissection?

Modified radical neck dissection is a comprehensive nodal dissection that spares at least 1 of the following structures: sternocleidomastoid, jugular vein, spinal accessory nerve, or submandibular gland.

What is considered a selective neck dissection?

Selective neck dissection is dissection of selective neck areas based on the understanding of the common pathways of spread according to the H&N site.

What is a supraomohyoid neck dissection?

Supraomohyoid neck dissection is removal of nodes above the omohyoid muscle (level I–III and sup V), common for cancers of the oral cavity (OC).

What is a lat neck dissection?

Lateral neck dissection is elective dissection of levels II–IV, traditionally for cancers of the larynx and pharynx.

What is an anterolat neck dissection, and when should it be done?

Anterolat neck dissection is elective neck dissection of levels I–IV, typically done for cN0 oropharyngeal cancer (OPC).

What is an ant neck dissection, and when should it be done?

Ant neck dissection is selective neck dissection of levels II–IV, typically done for cN0 laryngeal/hypopharyngeal cancers.

What is a posterolat neck dissection, and when is it done?

Posterolat neck dissection is elective neck dissection of the retroauricular, suboccipital, upper jugular, and post cervical nodes. It is used for skin cancers (squamous cell carcinoma, melanoma) located post to the ear canal.

What is an ant compartment dissection, and when is it done?

Ant compartment dissection is selective level VI dissection, traditionally performed for thyroid cancers.

image Workup/Staging


Which 3 H&N sites have the highest rates of clinical nodal positivity?

The nasopharynx (NPX) (87%), base of tongue (78%), and tonsil (76%) have the highest rates of clinical nodal positivity. (Lindberg R et al., Cancer 1972)

Which 2 H&N sites have the highest rates of retropharyngeal nodal positivity on CT/MRI?

On CT/MRI, nasopharyngeal and pharyngeal wall primaries have the highest rates of retropharyngeal involvement (74% and 20%, respectively). (McLaughlin MP et al., Head Neck 1995)

image Treatment/Prognosis


When is a selective neck dissection appropriate?

When there is a clinically negative neck but ≥10% risk of subclinical Dz; otherwise, do at least a modified radical neck dissection (rarely is a radical neck dissection done anymore).

Per NCCN guidelines, when is the omission of elective neck dissection appropriate after RT?

Per the NCCN, elective neck dissection may be omitted after a complete response of a cN1 neck.

When is an elective neck dissection necessary after definitive RT?

Elective neck dissection is necessary whenever there is a partial response/residual Dz after RT (any nodal stage).

When can an elective neck dissection be omitted for a pt with ≥N2 Dz?

This is controversial. The decision may be guided by PET response 10–12 wks after RT. If a CR, elective neck dissection may be left out. However, at some institutions, any pt with ≥N2 Dz would get neck dissection regardless of the response to RT.

What are the indications for adj RT after a neck dissection?

After a neck dissection, adj RT should be used with ≥3 cm +nodes, ≥2 + nodes, if ≥2 nodal levels are involved, with + ECE, or if there is an undissected high-risk nodal area.

When should chemo be added to PORT in the management of H&N cancers?

1.     Definite indications: +margin, +ECE (category 1 per the NCCN)

2.     Additional (weaker) indications: multiple nodes, PNI/LVI, T4a, or OC primary with level IV nodes (could consider chemo or just RT alone)

How should cisplatin be dosed when given with RT for H&N cancers?

The cisplatin dosing with RT is 100 mg/m2 intravenously on days 1, 22, and 43.

How did the 2 seminal H&N trials supporting the addition of chemo to RT in the adj setting differ, and what did they show?

EORTC 22931 (Bernier J et al., NEJM 2004): 334 pts randomized to PORT 66 Gy vs. PORT + cisplatin 100 mg/m2 on days 1, 22, and 43. Eligibility: ECE, +margin, PNI, LVI, and level 4–5 +N from OC cancer/OPC. There was better OS, DFS, and 5-yr LC with CRT but ↑ grade 3–4 toxicity.

RTOG 95-01 (Cooper JS et al., NEJM 2004): 459 pts randomized to 60–66 PORT vs. PORT + cisplatin 100 mg/m2 on days 1, 22, and 43. Eligibility: >2 LNs, ECE, +margin. There was better DFS (43% vs. 54%) and 2-yr LRC (72% vs. 82%) but only a trend to improvement in OS (57% vs. 63%).

What are the presumed reasons why EORTC 22931 showed an OS benefit while RTOG 9501 did not?

The EORTC trial included more margin+ pts (28% vs. 18%), more pts with worse tumor differentiation (19% vs. 7%), more hypopharynx cases (20% vs. 10%), and more pts that started RT ≥6 wks after surgery (32%).

What important study compared preop RT to PORT for advanced H&N (mostly hypopharyngeal) cancers?

RTOG 73-03 (Tupchong L et al., IJROBP 1991): 354 pts, 50 Gy preop vs. 50–60 Gy postop. LC improved with PORT but not OS. Both LC and OS improved with PORT in OPC pts.

What are the indications for boosting the tracheostomy stoma with PORT?

Indications for boosting the stoma with PORT:

1.     Emergency tracheostomy/tracheostomy prior to definitive surgery

2.     Subglottic extension

3.     Ant soft tissue extension

4.     T4 laryngeal tumors

What are the dose recommendations for PORT to the neck and primary?

In 2 Gy/fx: undissected clinically negative area, 50 Gy; postop (−margin), 60 Gy; postop (+margin, +ECE), 66 Gy; gross residual, 70 Gy

When should the retropharyngeal nodes be covered/irradiated?

Nasopharyngeal, hypopharyngeal, and pharyngeal wall primaries or ≥2 + nodal levels (N2-N3) all merit irradiation of the retropharyngeal nodes.

What are the indications for treating the sup mediastinal nodes in H&N cancer?

T3-T4, hypopharyngeal/thyroid primaries, and involvement of the supraclavicular nodes are indications for treating the sup mediastinal nodes.

What is the inf extent of the RT fields if sup mediastinal nodes are to be treated?

The inf extent encompasses nodes to the level of the carina or 5 cm below the clavicular heads.

What are some contraindications to neck dissection as the primary management of the neck in pts with H&N cancers?

Base of skull invasion, satellite skin nodules/dermal invasion, and medically unstable/inoperable pts. Relative contraindications include internal carotid invasion, bone invasion, and skin ulceration.

What did the TROG 98.02 study suggest regarding the utility of planned neck dissections after definitive CRT for H&N cancer?

TROG 98.02 determined that neck dissection may not be needed for N2-N3 pts who have a CR on PET 12 wks post CRT. These pts have low rates (4%–6%) of LRF despite the omission of neck dissection. (Corry J et al., Head Neck 2008)

image Toxicity


What are some common late sequelae of RT (+/+ neck dissection) in H&N cancer?

Neck fibrosis/scarring, submental edema, hypothyroidism, and xerostomia

According to the RTOG combinatorial analysis, what factors were associated with severe late toxicity after CRT in advanced H&N cancer pts?

Per the RTOG combinatorial analysis, advanced age, advanced T stage, laryngeal/hypopharyngeal primaries, and neck dissection were all associated with severe late sequelae after CRT. (Machtay M et al., JCO 2008)