b) Preauricular

Preauricular lesions are higher risk, and those with additional risk factors are more likely to locally recur. Surgery in this region for larger lesions is also likely to be cosmetically significant.

Assessment

Evaluate the extent of disease, including any spread along the external auditory canal. Invasion into the base of skull or ear cartilage indicate more aggressive lesions. Evaluate for any perineural spread. If there is concern, consider pre-treatment CT or MRI to evaluate the base of skull. Biopsy should be performed to confirm diagnosis.

Issues

Surgery is the treatment of choice in this region as the underlying temporo-mandibular joint may be adversely affected by radiotherapy leading to trismus or pain. Small lesions should be removed surgically in younger patients and those suitable for surgical excision.
In larger lesions with high risk of recurrence,
Radiotherapy is indicated those for whom surgical is not suitable. The usual factors apply:

  • Patient factors (unfit for surgery, refuse surgery, age)
  • Tumour factors (smaller tumours easier as less dose to TMJ)
  • Treatment factors
    • Single modality treatment is best for small lesions (< 2 cm)
    • Multiple modality therapy may be indicated for larger lesions (> 2 cm)

Radiotherapy options

Definitive

Definitive radiotherapy should be offered where surgery is not possible (pt refusal, other patient factors) or as an option for larger lesions that would have a poor cosmetic outcome (large flaps, loss of pinna).
Superficial x-rays are suitable for thin lesions 1-2 mm thick.
Orthovoltage x-rays are not suitable due to increased dose deposition in the temporal bone and temporo-mandibular joint.
Electrons are a suitable therapy in this region. Megavoltage photons would be acceptable in a wedge pair or 3D conformal arrangement.

Adjuvant

Postoperatively, patients should be offered radiotherapy when there is a high risk of local recurrence.

  • T4 tumours
  • Positive margins, further excision not possible
  • Perineural invasion
  • Skull base invasion
  • Poorly differentiated lesions with close margins < 5 mm

Electrons would be the ideal choice for close or positive margins. Superficial photons have insufficient penetration, and megavoltage photons would not be needed except for cases of perineural invasion.

Treatment Description

Definitive, Kilovoltage X-Rays

Definitive, Electrons

Adjuvant, Wedge Pair


Links