Salivary Glands Cancer

By

Osama El-Zaafarany

Epidemiology • Salivary gland neoplasms account for 6% of H&N

cancers (35% are malignant).

• Less than 0.3% of all malignancies.

• Approximately 80% of all salivary gland neoplasms originate in the parotid.

• The male-to-female ratio for malignant salivary gland tumors is 0.6.

• About 25% of parotid, 40% of submandibular, and

75% of sublingual gland tumors are malignant.

Etiology • Lifestyle: Cigarette smoking has a strong association

with Warthin’s tumor, a benign tumor of the parotid gland

• Occupational: Hairdressers, rubber manufacturing, exposure to metal in the plumbing industry and nickel compounds, and woodworking in the automobile industry

• Ethnic: Inuit men and women have the highest incidence rate of salivary gland cancer in the world, primarily from an excess of lymphoepithelial carcinomas

• Ionizing radiation: (including 131l): risk factor mostly for mucoepidermoid carcinomas and Warthin’s tumors. An increased risk has also been observed for adenocarcinomas among Hodgkin lymphoma survivors.

• Epstein-Barr virus: lymphoepithelial carcinomas

Anatomy

Pathology

WHO 2005 classification of malignant salivary epithelial tumors

Natural History • Mucoepidermoid carcinoma is the most common

malignant diagnosis (33%), followed by adenoid cystic carcinoma (24%), polymorphous low-grade adenocarcinoma, carcinoma ex pleomorphic adenoma.

• Mucoepidermoid carcinoma has higher incidence for LNs metas.

• Adenoid cystic carcinoma: 25-50 % distant metas.

PNI.

Needs adjuvant RTx.

Not respond to Taxol.

Regional lymph node metastases

• Mainly to levels II & III.

• This figure shows the percentage of LNs metas in Parotid gland cancers:

Risk of positive neck nodes according to summation of scores and site:

Workup

• H&P with bimanual palpation. Carefully examine cranial nerves and for trismus.

• CT and/or MRI of head and neck.

• PET scan is still investigational for salivary gland cancers.

• Fine-needle aspiration biopsy.

• Chest X-ray.

• Dental evaluation prior to the start of RT.

Staging

Treatment Recommendations

• Surgery forms the mainstay of defnitive treatment for salivary gland malignancies.

• Complications of surgery include facial nerve dysfunction and Frey’s syndrome; (gustatory flushing, sweating, auriculotemporal syndrome(.

• Superfcial parotidectomy can generally be performed for: low-grade parotid tumors.

T1–T2 superficial parotid lobe tumors without facial nerve invasion.

• Neck dissection recommended for: clinically +ve LNs.

high-grade tumors.

• Indications for post-op RT are currently controversial as there is no randomized data analyzing the role of post-op RTx.

• Consider post-op RTx for: PNI. close/+ve margins. high-grade tumors. T3-4 tumors. +ve LNs. +ve Vascular invas.

• RT alone (definitive) is indicated for medically inoperable and unresectable tumors.

• LC rates with RTx alone range from 20-80%.

• Neutron therapy may achieve better LC for unresectable or inoperable tumors.

• Brachytherapy or intraoperative RT can be considered for recurrent tumors.

• IMRT reduces mean doses to normal structures and allows dose-escalation to tumor.

RTx dose

• Post-op RT :

-ve margins: 60–63 Gy at 1.8–2 Gy/fx

+ve margins: 66 Gy at 1.8–2 Gy/fx

for gross residual disease: 70 at 1.8–2 Gy/fx

• RT alone (definitive): 70 at 1.8–2 Gy/fx

• Elective neck RT: 50–54 Gy at 1.8–2 Gy/fx. Ipsilat.

Levels I-II-III.

For tumors > 4cm include levels IV, V.

Field Arrangements (Parotid Gland Tumors)

• Two traditional radiation therapy techniques for parotid gland tumors; unilateral anterior and posterior wedge pair fields using either: 4-6 MV photons or 60Co.

12-16 MeV electron (80% of dose)

in combination with 4-6MV or 60 Co photons (20% of dose).

• Target:

Metastatic disease

• CAP regimen: cyclophosphamide (500 mg/m2), doxorubicin (Adriamycin; 50 mg/m2), and cisplatin (Platinol; 50 mg/m2) on first day of a 28-day regimen.

• The objective response rates to chemotherapy are modest, ranging from 15 to 50%, and lasting from 6 to 9 months.

• Paclitaxel 200 mg/m2 every 21 days (no response in adenoid cystic carcinoma)

• Targeted therapy may prove useful in the future as some histologies express EGFR, C-kit, and/or HER-2

Evidence

Role of adjuvant RTx: Dutch Head and Neck Cooperative Group (NWHHT), 2005:

Role of neutron RTx:

University of Washington, 2003:

Role of Elective Neck Irradiation

University of California, San Francisco (UCSF), 2007:

Follow-Up

• H&P:

every 1–3 months for 1 year.

every 2–4 months for second year.

every 4–6 months for years 3–5.

annually thereafter.

• Regular head imaging with MRI and CXR as indicated.

• TSH every 6–12 months if neck irradiated.