These tumors regardless of stage should be managed surgically upfront.
Indications to add adjuvant radiation are:
- Grade 3 tumor
- Positive margins
- Positive lymph nodes
- Tumor > 4 cm
- Adenoid cystic histology
Indications to add ipsilateral neck irradiation include:
- Grade 3 tumor
- Tumor > 4 cm.
Remember to cover cranial nerves VII (parotid) or V3 (submandibular) up to the skull base for adenoid cystic histologies.
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As a general rule of thumb, the smaller the salivary gland, the greater the chance that a tumor is malignant. Submental (80%) > submandibular (80%) > parotid (20%).
Parotid gland tumors are mostly benign adenomas. These tumors can be resected and observed without additional treatment. The deeper and the more posterior a tumor is located in the parotid, the more likely it is malignant.
As part of the work up of a salivary gland mass, the patient should have a full history and physical. Initial workup includes a CT neck and chest. A FNA biopsy sent to cytology (to improve diagnostic rate). An MRI to help delineate and soft tissue extension. General blood work including a CBC, RFTs, LFTs, TSH and electrolye panel.
Staging:
T1: < 2 cm
T2: 2 - 4 cm
T3: > 4 cm
T4a: Invades mandible, ear canal, facial nerve
T4b: Encases carotid, invades skull base or pterygoid plates
N1: Single LN <> 6 cm
Stage I = T1N0
Stage II = T2N0
Stage III = T3N0, T1-3N1
Stage IVa = T4aN0, T4aN1, T1-4aN2
Stage IVb = T4bNx, TxN3
Stage IVc = TxNxM1
Surgery
Malignant salivary gland tumors are resected with margins > 5 mm as initial management. A full neck dissection is not required if elective nodal irradiation is planned. Parotid tumors should have a level IIA neck dissection. For submandibular gland tumors, a neck dissection can be considered for high grade or large tumors.
Adjuvant Radiation
Adjuvant radiation is indicated for:
- High grade tumors
- Large primary tumors (T3 or T4)
- Positive margins
- Positive lymph nodes
- Adenoid cystic or Squamous cell histology
Elective nodal irradiation should be offered to:
- Tumors > 4cm (T3 or T4)
- High grade tumors (they harbor microscopic disease in 50%)
- Squamous cell histology (50% recurrence without XRT to ipsilateral neck).
Adenoid Cystic Carcinoma
UCSF reviewed their Adenoid cystic cases and found that T4 tumors, perineural invasion, major nerve involvement and omission of adjuvant radiation where all predictors of recurrence (this makes sense). Hence, all Adenoid cystic carcinomas should receive adjuant XRT. These tumors rarely recur locally or involve regional lymph nodes, so elective nodal irradiation should not be routinely offered. However, they have a tendency to spread perineurally along cranial nerves in 50% of cases. Treatment volumes should include the cranial nerves to the skull base. Cranial nerve VII should be included up to stylohyoid foramen in Parotid tumors. The lingual branch of cranial nerve V3 should be included up to it's entry in the skull base or Meckel's Cave (represented by the arrows in the figures below) in Submandibular tumors.
Radiation Dose
- Gross disease should be treated with 70 Gy in 35 fractions
- Positive margins or extracapsular extension should be treated with 66 Gy in 33 fractions
- Negative margin tumor bed should receive 60 Gy in 30 fractions
- Elective neck treatment should receive 50 Gy in 25 fractions.
Ideally, patients should be treated with IMRT techniques. If this is not available, wedge pair techniques are adequate when the volume to treat has a depth less than 7 cm. Otherwise, you can consider a mixed photon/electron technique.
Complications:
Xerostomia, cranial nerve paresthesia
Prognosis:
5 year overall survival
- Stage I = 75%
- Stage II = 60%
- Stage III = 50%
- Stage IV = 30%
Mucoepidermoid = 80% with radiation and 40% without radiation
Adenoid cystic = 75% with radiation and 25% without radiation
Most recurrences will occur distantly and not locally.
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