Issues
Surgery is difficult as there is minimal subcutaneous tissue. Cosmesis is difficult to maintain for larger lesions.
Radiotherapy is difficult as cartilage necrosis is an issue and the ventral surface is irregular. Dorsal ear lesions may have a more flattened surface.
These lesions behave more aggressively and are be upstaged to T2 if another high risk feature is present (deep or perineural invasion, poorly differentiated).
Choice of treatment
Small lesions can be removed surgically using a wedge excision. Adjuvant radiotherapy is indicated if high risk features are present.
Larger lesions can be treated with removal of the ear or with radiotherapy.
Other treatment options (imiquimod, 5-fluorouracil, curettage) are not appropriate at this site.
Choice of Radiotherapy Modality
Small lesions on the posterior surface of the ear, with < 5 mm thickness, can be adequately treated with lower-energy kilovoltage x-rays (50-100 kV). Higher energies lead to increased dose deposition in cartilage and bone which is contraindicated.
For larger lesions, electrons are generally indicated as they have better penetration at depth and reduced dose deposition in bone compared to kilovoltage x-rays.
Very large lesions with skull base involvement may be treated with megavoltage photon beam therapy, most likely with a wedge pair or 3D conformal technique.
Radiotherapy Technique
Kilovoltage Photons
- Treat the patient with curative intent, using radical radiotherapy employing kilovoltage x-rays.
- Pre-simulation, obtain informed consent.
- Clinical markup. Palpate the tumour and mark the palpable extent. Add a 0.5 cm margin (unless high risk features, then use 1 cm). If the surface is irregular, then conversion to an electron based technique should be done.
- Depending on the shape of a the lesion, either use a standard cutout or custom cutout.
- Prescribe a total dose of 50 Gy in 20 fractions (or 60 Gy in 30 fractions).
Electrons
- Treat the patient with curative intent, using radical electron beam radiotherapy.
- Pre-simulation, obtain informed consent.
- At simulation, palpate the tumour extent. Add a 1 cm expansion to account for microscopic disease and the electron penumbra (1.5 cm if high risk features). Finally, pack the pinna, the space between the dorsal earlobe and scalp, and external auditory canal with bolus. Add 0.5 cm of buildup bolus if low energy electrons are to be used to ensure adequate dose at skin surface. For complex lesions, CT simulation may be done.
- A pre-forged or custom cutout should be used.
- Prescribe a total dose of 55 Gy in 22 fractions (or 64 Gy in 32 fractions).
Megavoltage Photons
- Treat the patient with curative intent, using radical radiotherapy employing megavoltage x-rays.
- Pre-simulation, obtain informed consent.
- At simulation, palpate the extent of the tumour. Add a 0.5-1 cm expansion based on the tumour features (likely 1 cm if megavoltage photons are required!) and wire this border as the CTV. Apply bolus to remove contour irregularities of the ventral earlobe * and eliminate the air gaps in the external auditory canal and the space between the ear and scalp. Apply 1 cm of blanket bolus to the entire region to ensure adequate dose buildup from megavoltage x-rays.
- Perform a CT scan through the region of interest (from vertex to suprasternal notch).
- Use 3D conformal radiotherapy. GTV = tumour visible on CT/wired area. CTV = 1 cm expansion from GTV, respecting air/tissue borders. If perineural invasion of a named nerve, trace the nerve from the tumour back to the base of skull (usually the trigeminal ganglion or the internal auditory meatus) as the nerve CTV. PTV = 0.5 cm expansion from CTV (both primary and nerve CTV if present).
- Dose = 64 Gy in 32 fractions. Can be complicated when the PTV extends into the cranial vault with respecting tissue tolerances around the cavernous sinus or brainstem.