Radiation Oncology: A Question-Based Review

86
Ear Cancer

Steven H. Lin and Vincent J. Lee

image Background


What structures constitute the outer and inner components of the ear?

1.     Outer ear: pinna (auricle), external auditory canal, tympanic membrane, and middle ear

2.     Inner ear: temporal bone (mastoid bone of bony and membranous labyrinth)

What is the lymphatic drainage of the ear?

The ear drains to the parotid, retroauricular, and cervical nodes.

What are the most common cancer histologies of the outer vs. the inner ear?

1.     Pinna: basal cell carcinoma

2.     Rest (canal, middle ear, mastoid): squamous cell carcinoma (SCC) (85%)

What % of pts with ear cancer present with nodal mets?

<15% of pts present with nodal mets.

image Workup/Staging


What is the general workup for tumors of the ear?

Tumor of the inner ear workup: H&P, otoscopy, LN exam, CT/MRI, tissue Bx, and audiometry

What staging system is used for cancer of the ear?

The AJCC nonmelanoma skin cancer staging −system is used for ear cancer (refer to Chapter 84).

For cancer of the ear, what are considered high-risk features per the latest AJCC edition?

DOI >2 mm, Clark level ≥IV, + PNI, and poor differentiation are considered high-risk features for cancer of the ear.

image Treatment/Prognosis


What is the general Tx paradigm for a pt with ear cancer?

Ear cancer Tx paradigm: surgery or definitive RT −(surgery preferred for cartilage invasion)

What features of the primary tumor merit consideration of elective LN irradiation?

Elective LN irradiation is considered for large tumors (>4 cm) and deep invasion of underlying −structures (i.e., cartilage).

How should SCC of the mastoid be treated?

SCC of the mastoid Tx: mastoidectomy or temporal bone resection → PORT

How are tumors of the pinna treated?

Tumor of the pinna Tx: electrons or orthovoltage RT (1-cm margin for <1-cm tumors; 2–3-cm margin for larger tumors)

How should tumors of the external auditory canal be treated?

External auditory canal Tx: Include in the Tx volume the entire external auditory canal and temporal bone with 2–3-cm margins, and include ipsi regional nodes (pre-/postauricular, level II); these tumors should be treated to 60–70 Gy.

How should the RT doses be modified based on tumor size?

Conventional fx of 1.8–2 Gy:

1.     Small thin lesions < 1.5 cm: 50 Gy

2.     Larger tumors: 55 Gy

3.     Min cartilage/bone involvement: 60 Gy

4.     Cartilage/bone involvement: 65 Gy

When should higher-energy electrons be used for ear lesions?

Higher-energy electrons should be used for large, deep, unresectable tumors (to cover the deepest extent).

image Toxicity


What is the max dose allowed in order to minimize the likelihood of osteoradionecrosis?

Osteoradionecrosis can be minimized by keeping bone doses to <70 Gy (~10% rate for doses >65 Gy).

What are some compli−cations in the Tx of the ear with RT?

RT complications include osteo- or cartilage −necrosis, hearing loss, chronic otitis, and xerostomia.