Epidemiology:
Malignant disease of the ear is rare. External ear tumors most commonly occur in patients 50 to 80 years old and are more common in men while tumors of the middle ear and mastoid are more common in patients 40 to 60 years old with more women having middle ear tumors than men.2
Etiology:
Tumors of the external ear are often cutaneous malignancies that could be related to sun exposure. "Other predisposing factors described, although their significance is in question, are otorrhea, chronic exzema, chronic dermatologic conditions, and chronic ulcerations from trauma."2
Signs & Symptoms:
The #1 symptom is pain. Chronic inflammation, chronic drainage, or a perforated eardrum that will not heal can also be symptoms of inner ear or mastoid cancer.3 Basal cell carcinoma presents as small ulcerations that can grow and invade deeply destroying the ear if left untreated.1
Diagnostic Procedures:
The diagnostic work up should include a high resolution CT and MRI. The CT will help determine if the tumor is resectable. The MRI provides excellent delineation of soft tissue tumor margins, muscle infiltration, intracranial extension, and vessel encasement. A biopsy is always needed for diagnosis.1
Histology:
85% of tumors involving the auditory canal, middle ear, and mastoid area are Squamous cell carcinoma. Carcinoma of the external ear is usually Basal cell carcinoma.1
Lymph Node Drainage:
Lymphatic vessels of the tragus and anterior-exterior portion of the auricle drain into the superficial parotid lymph nodes. Lymphatic vessels of the posterior-exterior and whole cranial aspect of the auricle drain into the retoauricular lymph nodes, whereas those of the lobule drain into the superficial cervical group of lymph nodes. Lymphatics from middle-ear and the mastoid antrum pass into the parotid nodes and the upper deep cervical lymph nodes. Lymphatics in the middle ear and eustachian tube are sparse, but the inner ear has no lymphatics. 1
Metastatic Spread:
Usually there is no systemic metastatic spread of the disease. Local extension of the primary tumor can occur. 1
Grading:
The following is the histopathologic Grade for Basal Cell and Squamous Cell Carcinoma of the Skin (including external ear).5

Histopathologic Grade (G)

Gx -Grade cannot be assessed
G1- Well differentiated
G2- Moderately differentiated
G3- Poorly differentiated
G4- Undifferentiated

Staging:
-Neither the American Joint Comittee nor the International Union Against Cancer has a staging system for tumors of the ear.
-Stell and McCormick have proposed a staging system using the International Union Against Cancer guidelines:

T1: Tumor limited to site of origin, with no facial nerve paralysis and no bone destruction detected
radiographically.
T2: Tumor extending beyond site of origin, indicated by facial paralysis or radiographic evidence of bone
destruction but no extension beyond organ of origin.
T3: Clinical or radiographic evidence of extension to surrounding structures (e.g. dura, base of skull, parotid
gland, temporomandibular joint).
TX: Insufficent data for classification, including patients previouly seen and treated eleswhere.
1
Radiation Side Effects:
Radiation Sequelae include cartilage necrosis of the external auditory canal and osteoradionecrosis of temporal bone. overall 4% to 10% incidence of bone necrosis can be expected after administration of 60 to 65 Gy. Risk of necrosis increases for lesions larger than 4 cm. 1
Prognosis:
External ear lesions are more easilly controlled than those of the middle ear or mastoid. They are also diagnosed sooner and since they are mostly cutaneous, surgery and radiation therapy are usually effective. Large middle ear lesions that have extension into the temporal bone are the most difficult to treat. "There does not appear to be a correlation between degree of tumor differentiation and survival, although it may serve as a predictor for local control in tumors involving the petrous temporal bone." Middle ear tumors that have associated seventh nerve palsy is an indicator for poor local control. If there is spread of the tumor to the lymph nodes, there is a poor prognosis because that is usually something that happens late in the course of the disease.2
Treatments:
External Ear
External ear tumors are most often treated with limited surgery or external radiation therapy. If the tumor is in the early stages it will usually be treated with orthovoltage or electron beam therapy. Surgery is beneficial if the lesion has invaded the cartilage or extends medially into the auditory canal. Interstitial irradiation using afterloading iridium 192, for tumors smaller than 4 cm, offers excellent local control with good cosmetics. Radical surgery and postoperative irradiation are the accepted methods of treatment for more advanced lesions of the external auditory canal and lesions in the middle ear and mastoid. Lesions of the outer part of the auditory canal require local excision with a margin of at least 1 cm between the lesion and the tympanic membrane if there is no radiographic evidence of invasion of the mastoid. When the tumor involve the bony auditory canal and impinges on the tympanic membrane, but does not involve the middle ear or the mastoid, a partial temporal bone resection may be necessary.

Middle Ear and Temporal Bone
Depending on the extent of the tumor, surgical options include mastoidectomy, lateral temporal bone resection, subtotal temporal bone resection, and total temporal bone resection. Postoperative irradiation is important to increase the chance of local tumor control.

Radiation Therapy Techniques
Tumors involving the pinna can be treated with electrons or with superficial or orthovoltage irradiation. The fields can be round or polygonal, and are drawn around the tumor to spare surrounding normal tissues. For small, superficial tumors, margins of 1 cm are adequate. Large extensive lesions can encompass the entire pinna or external canal, with 2 to 3 cm margins around the tumor. Lesions involving the pinna should be treated with low fractionation (1.8 - 2 Gy daily). Doses of 65 Gy over 6.5 weeks are required to achieve adequate tumor control. Large lesions of the external auditory canal may be treated with irradiation alone or combined with surgery. The fields should include the entire ear and temporal bone with an 3 cm margin. The volume treated should include the ipsilateral preauricular, postauricular, and subdigastric lymph nodes. Extremely advanced, unresectable tumors should be treated with high-energy ipsilateral electron beam therapy (16 to 20 MeV), either alone or mixed with photons (4 to 6 MV), or with wedge-pair techniques using low energy photons. Doses of 60 to 70 Gy over 6 to 7 weeks are required. 1


ear_portal.JPG
Figure 1. Treatment portal for tumor of the middle ear involving the petrous bone. The mastoid is included in the treatment volume.2
middleearisodose_distributionnew.JPG
Figure 2. Isodose distribution for middle ear tumor using photons and electrons.
2
TD5/5:
TD 5/5
Spinal Cord - 4500 cGy
Retina - 5500 cGy
Cornea - 5000 cGy
Lens - 500 cGy
Optic Chiasm - 5000 cGy
Optic Nerve - 5000 cGy
Ear (middle) - 5000 cGy
Ear (vestibular) - 6000 cGy
Pituitary Gland - 4500 cGy
Skin - 4500 cGy 4

References:
1. Chao KS, Perez CA, Brady LW. Radiation Oncology Management Decisions. 2nd edition. Philadelphia,PA: Lippincott, Williams & Watkins. 2002:183-185,186-187.
2. Perez CA, Brady LW, Halperin EC, Scmidt-Ullrich RK. Principles and Practice of Radiation Oncology. 4th editiion. Philadelphia, PA: Lippincott, Williams, & Wilkins. 2004: p. 897.
3. Ear surgery.org. http://www.earsurgery.org/site/pages/learn/ear-tumors-of-the-middle-ear.php : accessed Jan. 13,2010
4. Washington,C.M & Leaver, D.(Eds.).(2004). Principles and Practice of Radiation Therapy (Second ed). St. Louis, Missouri; Mosby Inc: pg. 80-81.
5. Murphy GP, Lawrence W, Lenhard RE. American Cancer Society Textbook of Clinical Oncology. second edition. Atlanta, GA: The American Cancer Society, Inc. 1995; 332.