Pocket Oncology (Pocket Notebook Series), 1st Ed.

SALIVARY GLAND TUMORS

Eric L. Smith and Alan L. Ho

Definition

• Malignant tumors such as mucoepidermoid carcinoma and adenoid cystic carcinoma, arising from the major salivary glands include the following.

Parotid (85%)

submandibular

sublingual

• Minor salivary glands (many of w/c are on the hard palate)

• Less frequent: Adenocarcinoma, acinic, malignant myoepithelial tumors, SCC, & others

Epidemiology

• 6–8% of H&N CA

• 2000–2500 cases/y in US

Risk Factors

• Radiation, Smoking (Warthin Tumor, benign), HIV, EBV (lymphoepithelial carcinoma)

Poor Prognostic Factors

• High histologic grade, large tumor size, local invasion including PNI & LVI

Genetics

• MEC: t(11;19): MECT1-MAML2 fusion; EGFR overexpression

• ACC: t(6;9): MYB-NFIB fusion leading to overexpression of many c-myb targets including VEGFA, KIT, FGF2, & BCL2 all of w/c are potential therapeutic targets (PNAS 2009;106:18740). Also commonly expressed are NCAM, NGF, & TrkA w/c may explain its proclivity for PNI.

Historical Clinical Subtypes

MEC:

ACC: Tubular (grade 1), cribriform (grade 2), solid (>30% solid = grade 3)

Diagnosis

• H&P inc fiberoptic exam

• CT/MRI base of skull to clavicle in adv CA

• Chest imaging w/CXR or CT

• FNA

General Staging

• Stage I: ≤2 cm w/o extraparenchymal extension

• Stage II: 2–4 cm w/o extraparenchymal extension

• Stage III: >4 cm and/or extraparenchymal extension and/or + LN <6 cm

• Stage IV: Invades skin, mandible, ear canal, facial nerve, skull base, encases carotid art, and/or LN >6 cm, and/or distant met (stage IVC)

Localized Disease (Stage I–IVB) Management

• Complete surgical resection if possible For parotid tumors, w/preservation of facial nerve as goal if it is not directly involved in the tumor

• Consider post-op RT: While there is no prospective data this is often done if intermediate-high grade, or low grade plus any 1 of: PNI, pos margins, or tumor spillage, or any ACC

Locoregional Recurrence Management

• If resectable: Salvage w/surgery, although outcomes are disappointing

• If not resectable: RT for selected pts, although re-recurrence is common

• If pt is not appropriate for surgery or RT: Treat as met disease

Metastatic Disease (Stage IVC) Management

• Most commonly to lung, liver, & bone (bone signifies more aggressive disease)

• While there is a wide range, median survival for ACC is 3 y

• Unclear if chemo alters course of disease, use mainly for palliation of disease-related sx

• Recommendations are based on small phase I–II trials

• ACC: Potentially active single agent tx w/anthracycline, vinorelbine, or cisplatin. Combination tx can potentially result in higher RR, but unclear if there is any overall advantage over single agent Rx. Value of second-line Rx is unproven (Lancet Oncol 2011;12:815)

• MEC: Cyclophosphamide, doxorubicin, & cisplatin (CAP) ± 5-FU combination Rx is most widely studied w/ORR of 40–50%, mostly stabilization of disease lasting 3–7mos (Cancer 1987;60:2869). Single agent choices: Those mentioned for ACC above or paclitaxel

Molecular Targeted Therapy

• KIT targeted by Imatinib, no objective responses (Oral Oncol 2007; 43:33)

• EGFR targeted by Cetuximab, no objective responses, 67% stabilization for median 6 mos; & Gefitinib no objective responses (JCO 2006;24:2673)

• EGFR/HER2 targeted by Lapatinib no objective responses, 36% stabilization of >6 mos (JCO 2007;25:3978)

• VEGFR, PDGFR, MYB, AKT are all rational targets under active investigation for ACC.