The management of benign and malignant tumours is significantly different.
Benign Salivary Gland Tumours
Pleomorphic Adenoma
The mainstay of treatment for this benign tumour is surgical excision. Surgical excision should be a superficial parotidectomy as there is significant risk of recurrence with enucleation (due to deficiencies of the capsule).
Radiotherapy to the parotid gland is indicated only when:
- There are positive surgical margins and significant risk to the facial nerve with re-excision
- Local recurrence unable to be treated surgically (usually after a second recurrence)
- Tumour spill during surgery
Dose is typically 50 Gy in 25 fractions delivered to the residual parotid.
Warthin Tumour
This benign tumour is well encapsulated and surgical excision is usually curative. Local recurrence is very uncommon. Radiotherapy for Warthin tumour is poorly described; case reports delivering similar doses to pleomorphic adenoma have met with good outcomes.
Malignant Salivary Gland Tumours
Primary Treatment
Surgery should be considered in almost all cases as the first therapy. It provides better local control. For very advanced lesions, or lesions that involve functional components of the head and neck (eg. facial nerve), the decision to proceed with surgery can be more complex.
Primary radiotherapy is delivered to a dose of 70 Gy in 35 fractions to the tumour. Regional nodes may be included if pathologically involved or at high risk of subclinical involvement (eg. poorly differentiated tumour, tumour > 4 cm, etc), in a similar manner to squamous cell carcinoma of the head and neck.
Adjuvant radiotherapy is more complex. It is recommended when there is a high risk of recurrence:
- Recurrent disease
- Positive or close margins
- T3 or T4 tumours
- Perineural invasion of named or unnamed nerves
- Involvement of adjacent structures (including skin, bone)
- Adenoid cystic carcinoma subtype has a higher rate of local recurrence and radiotherapy should be considered more strongly in this group
Total dose should be 60 Gy except in cases of positive margins in which case 66-70 Gy should be employed to the tumour bed. Adenoid cystic carcinoma, or other carcinomas which show pathological evidence of perineural invasion, should have the nerves supplying the tumour bed irradiated back to the skull base (typically nerves V1, V2, V3 or VII).
Nodal treatment
Lymph node metastases are less predictable for salivary gland tumours. Treatment of the neck should always happen when there is clinically evident or PET positive disease. Elective treatment of the neck (neck dissection or 50 Gy) should be considered for:
- T2 or greater tumours
- Lymphovascular invasion
- High grade tumours
Parotid: Treat IB, II, III, IV. Consider V if there is clinical lymph node involvement.
Submandibular: Treat IB, II, III, IV
Sublingual: Treat IA, IB, II, III, IV
