Malignancies of the Major Salivary Glands

TITLE: Malignancies of the Major Salivary Glands
SOURCE: Grand Rounds Presentation, UTMB, Dept. of Otolaryngology
DATE: May 23, 2007
RESIDENT PHYSICIAN: = Chad Simon, MD
FACULTY PHYSICIAN: Susan D. McCammon, MD
SERIES EDITORS: Francis B. Quinn,= Jr., MD and Matthew W. Ryan, MD

"This material was prepared by resident physicians in partial fulfillment of educational requirements established for the Postgraduate Training Program = of the UTMB Department of Otolaryngology/Head and Neck Surgery and was not intended for clinical use in its present form. It was prepared for the purp= ose of stimulating group discussion in a conference setting. No warranties, eit= her express or implied, are made with respect to its accuracy, completeness, or timeliness. The material does not necessarily reflect the current or past opinions of members of the UTMB faculty and should not be used for purposes= of diagnosis or treatment without consulting appropriate literature sources and informed professional opinion."

Epidemiology

It is estimated that 1 in 100,000 U.S. residents will develop a salivary malignancy at an average age of 56.6 year= s of age. The most common malignant histology is Tumors of the submandibular and sublingual salivary glands are more likely to be malignant than those in the parotid. Employment in the rubber industry, exposure to nickel alloys, exposure to silica dust, and the use of kerosene as cooking fuel have been associated with an increased risk of a primary salivary malignancy. A history of skin cancer has also been found t= o be associated with subsequent development of a primary salivary cancer when it originates in the scalp or face, it also presents a risk for metastases to = the parotid gland.

Diagnosis

Malignant salivary neoplasms present as a painle= ss mass in approximately 75% of patients. Rarely, patients are initially seen = with pain or facial nerve palsy. Though not definitive by any means, a palpable = mass arising in a salivary gland, associated with pain, and/or nerve paralysis is more likely to be malignant than benign. It is believed that episodic pain suggests continued obstruction, whereas constant pain is more suggestive of malignancy. Trismus, cervical adenopathy, fixation, numbness, loose dentiti= on, or bleeding also suggest the presence of malignancy.

With a clinical history and physical examination suggestive, physicians should seek to solidify the diagnosis before employi= ng treatment and before counseling a patient on prognosis. Traditionally, FNA = has been performed preoperatively for histologic confirmation of malignancy and= to aid in operative planning, such as planning for elective neck dissection. In 1997, Tew and others evaluated 195 FNAs and 159 intraoperative frozen secti= ons for parotid tumors. They found that FNA had a 90% sensitivity for malignanc= y if non-diagnostic biopsies were excluded. They also found that intraoperative = frozen section had a 96% sensitivity for malignancy. More recently, in 2005, Zbare= n et al reported on 83 patients with primary carcinoma of the parotid and clinic= ally negative necks. This group found that preoperative FNA yielded a 30% false-negative rate for malignancy. In contrast, intraoperative frozen sect= ion diagnosis yielded only 7% fal= se negative. These findings suggest that surgeons should consider the addition= of intraoperative frozen section to the diagnostic battery. An incisional biop= sy at a site that can be excised during the definitive surgery approximates 10= 0% accuracy and is therefore preferable in those patients in whom the extent of the surgery (e.g., no surgery, nerve sacrifice, total vs superficial parotidectomy) would change with a change in histologic diagnosis.

Imaging can add significantly to the diagnostic = workup of salivary malignancies. Ultrasound can provide guidance in obtaining fine-needle biopsy specimens from deep parotid or parapharyngeal space tumo= rs. In patients with cystic or heterogeneous masses, ultrasound ensures samplin= g of the solid component and may also be helpful in biopsy masses that are diffi= cult to palpate. Computed tomography (CT) with intravenous contrast is routinely used preoperatively and provides excellent detail of the tumor volume, its relation to vascular and bony structures, as well as surveillance of the regional lymphatics. Magnetic resonance imaging (MRI) provides excellent so= ft tissue detail, which is superior to that of CT and has the advantage of not requiring contrast for vascular detail or ionizing radiation. The usefulnes= s of PET scanning in the setting of salivary gland malignancy is yet to be clear= ly defined. Keyes and others performed preoperative PET imaging on 26 patients with parotid tumors. A PET scan accurately predicted the nature of the neop= lasm in 69%, demonstrated 100% sensitivity for malignancy, and a false-positive = rate of 30%. Roh et al, reported this year on thirty-four patients with newly diagnosed salivary gland cancers who underwent CT and 18F-FDG PET before surgical resection with radiotherapy. The diagnostic accuracies of CT and 18F-FDG PET for detecting primary tumors and neck metastases were compared = with a histopathologic reference. 18F-FDG PET was more sensitive than CT for the detection of cervical metastases (80.5% vs. 56.1%; P < 0.05) at initial staging.

Treatment

Ablative surgery has long been the mainstay of treatment of the primary tumor in salivary malignancies. Superficial parotidectomy has become the widely accepted form of intervention for most parotid tumors. A higher risk of facial nerve injury and the potential for intraoperative seeding of tumor resulting in recurrence of the tumor has be= en associated with the use of lesser procedures. Therefore, a superficial parotidectomy has been touted as the minimal surgery of the parotid gland. Overall, the safety of parotidectomy has been well established, and the complication rate remains low. Total parotidectomy may be necessary for tum= or extension into the deep parotid lobe or when the tumor primarily arises in = the deep lobe. This can be performed with preservation of the facial nerve. Occasionally, patients may require extended parotidectomy, which includes resection of the masseter muscle or the ascending portion of the mandible. Facial nerve sacrifice is not routinely advocated. Nerve preservation in primary salivary malignancy is recommended if the nerve is functioning norm= ally before surgery. Every attempt to dissect the tumor from the individual bran= ches should be undertaken. If tumor is completely encasing the nerve branches, neural sacrifice is limited to the involved branches. In general, tumors of= the submandibular gland require complete excision of the gland.

Postoperative radiation to the primary tumor bed should be considered. North et al reported in 1990 on 87 patients with carcinomas of the major salivary glands (70 parotid and 17 submandibular). = From 1975 to 1987, they were treated at Johns Hopkins by either surgery or surge= ry followed by postoperative radiotherapy (RT). For patients with previously untreated disease, 5 of 19 (26%) treated by surgery alone experienced local recurrence, whereas only 2 of 50 (4%) recurred locally following surgery pl= us postoperative RT (p =3D 0.01). The determinant 5-year actuarial survival for patients receiving postoperative RT was 75% versus 59% for surgery alone. T= hat same year, Armstrong et al, at Memorial Sloan Kettering reported on 46 pati= ents with previously untreated malignant tumors of major salivary gland origin received combined surgery and postoperative radiotherapy between 1966 and 1= 982. They were compared with 46 patients treated with surgery only between 1939 = and 1965, who were matched according to prognostic criteria. The 5-year determi= nate survival rates for patients given combined therapy with stage I and II dise= ase versus patients given surgery only was 81.9% versus 95.8%, while for stages= III and IV it was 51.2% versus 9.5%, respectively. Local control for stage III = and IV disease in patients given combined therapy versus patients given surgery only at 5 years was 51.3% vs 16.8%. For patients with nodal metastases, 5-y= ear determinate survival for the combined-therapy group versus the surgery-only group was 48.9% versus 18.7%, and the corresponding local-regional control = was 69.1% versus 40.2%. The results of this analysis suggest that postoperative radiotherapy significantly improves outcome for patients with stage III and= IV disease and for patients with lymph node metastases. Chen, in 2007, reporte= d on 207 patients who, over 5 decades, received surgery without XRT as primary modality. He identified patients who were at high risk of locoregional recurrence with surgery alone. Based on these observations, he recommended postoperative XRT for patients with T3-T4 disease, positive surgical margin= s, high grade tumor histology, or regional nodal metastasis.

There is little dispute that patients with clini= cal evidence of cervical nodal metastasis require treatment of the neck. Disput= e in the literature still exists, though on whether or not to treat clinically negative (N0) necks.

To begin, the risk of occult nodal disease is wi= dely varied in the literature. Armstrong et al studied the incidence of occult n= odal metastasis. Of 407 patients with clinically negative necks, neck dissection= was done in 90. Occult metastasis was found in 38% of these specimens. To attem= pt to determine incidence of metastasis related to prognostic factors, the researchers report incidence percentage using all patients with the factor present, even if they did not undergo neck dissection. The cancers with the highest incidence, broken down by histologic subtype, are 41%, 18%, and 14%= for epidermoid malignancy, adenocarcinoma, and mucoepidermoid, respectively. It= is important to note that mucoepidermoid was not divided into low and high gra= de histologies. Frankenthaler et al in 1992 reported their estimate of the incidence of occult neck metastasis in parotid cancer only. They retrospectively reviewed 99 charts of patients that had N0 necks and underw= ent neck dissection. Their overall incidence of occult neck nodes was 12%. By histology, the incidence was 80%, 50%, 25%, 17%, 10% for salivary duct, squamous cell, adenocarcinoma, undifferentiated, and mucoepidermoid cancer, respectively. Stennert, in 2003, reported on 160 consecutive patients over 4 years. At their institution, policy was to perform ipsilateral neck dissect= ion on all major salivary gland cancers, regardless of T stage or histology. Th= is allows evaluation of a true incidence of neck metastasis. This report found = the highest incidence in adenocarcinoma (17%) adenoid cystic cancer (16%), and mucoepidermoid cancer (13%).

Estimates can be made on the chance of a patient having subclinical nodal metastasis based on prior studies. Even with these estimates, it is not clear as to which patients should undergo elective neck dissection or elective neck irradiation. Appropriately treating the neck in salivary malignancy is important for patient outcomes. For instance, overal= l 5 year survival of patients with and without involvement of the regional node= s is estimated at 10% and 75% respectively for the parotid and 9% and 41% for the submandibular gland. Medina, in 1998, proposed a rationale for neck dissection on N0 necks. He proposed = that patients that have factors that are indications for post-operative radiation are also the same ones that are at high risk for nodal metastasis and that these patients should simply undergo neck irradiation simultaneously and fo= rego neck dissection. Medina emphasized that, at the time of his report, the effectiveness of XRT on controlling neck disease had not been studied. In 2005, Zbaren et al report= ed on 83 patients with primary carcinoma of the parotid and N0 necks. Two treatment groups were studied, one underwent neck dissection, the other was observed. Of note, no strict criteria were used to select patients for one = or the other treatment modality and no significant imbalance was found between= the 2 groups with respect to demographic, clinical, and pathological variables = and treatment modalities of the primary carcinoma. Occult metastases were detec= ted in 8 (20%) of 41 cNO staged patients who underwent elective neck dissection= . Among these patients, 5 had a high-grade carcinoma and 3 had a low-grade carcinom= a. The primary carcinoma of these 8 patients was classified as T2 in 4, as T3 = in 1, and as T4 in 3 cases. Regional recurrence occurred in none of the patien= ts with an elective neck dissection and in 7 patients in the “observation” group (17%) (P =3D 0.006). Of the 7 patien= ts without neck dissection and neck recurrence, 2 patients were initially given adjuvant radiotherapy to the neck. The actuarial and the disease free survi= val rates at 5 years for patients with neck dissection were 80% and 86% and 83%= and 69% for patients without neck dissection. Based on this study, the authors dispute Medina’s treatment paradigm and recommend elective neck dissection in all primary parotid carcinomas. Chen and others reported in 2006 on 251 patients with clinically N0 necks who received postoperative radiation therapy after gross total tumor resection. Their results showed that none of the 131 patients w= ho received ENI had neck failure compared with 24 of 120 who did not receive E= NI. The corresponding 10-year estimates of nodal relapse were 0% and 26%, respectively (p =3D 0.0001). Notably, there were no significant differences in the distribution of clinical and disease characteristics with respect to age, perineural invasion, T-stage, and primary site, among patie= nts treated with and without ENI. The highest crude rates of nodal relapse among those treated without ENI were found in patients with squamous cell carcino= ma (67%), undifferentiated carcinoma (50%), adenocarcinoma (34%), and mucoepidermoid carcinoma (29%). There were no neck relapses among patients treated either with or without ENI for patients with adenoid cystic or acin= ic cell histology. It is clear that, for many patients with clinically N0 neck= s, based on histology, the risk of harboring occult disease in the regional ly= mph nodes is low enough that ENI is not warranted. Patients with adenocarcinoma= or mucoepidermoid carcinoma appear to be at increased risk for developing nodal relapses without neck treatment, and ENI should strongly be considered for these histologies. These findings also demonstrate that it is reasonable to= use ENI as an alternative to neck dissection and should be considered, especial= ly if postoperative radiation will be administered to the primary tumor.

Conclusions

Malignancies of the major salivary glands repres= ent a rare and diverse group of cancers. Knowledge about tumor staging and histol= ogic grading is necessary for prognostic predictions, patient counseling, and treatment planning. Surgical treatment should be the primary therapy with removal of all gross disease as the surgical goal. Patients should receive postoperative radiation to the primary site if the tumor is stage III or IV= , or if the pathology shows positive margins or perineural invasion. Careful consideration must be given to treatment of the neck, with clinical disease= as definite indication for neck dissection and/or neck irradiation. Patients w= ith N0 necks may have a higher incidence of occult metastasis than previously thought. Consideration should be given for elective neck dissection or elec= tive neck irradiation in the N0 neck, especially with high incidence of occult n= eck metastasis based on histology and stage. Strong evidence suggests that radiation therapy is effective at controlling neck disease and consideration should be given to elective neck irradiation in lieu of neck dissection. Fu= ture studies are needed to compare outcomes of elective neck irradiation versus = elective neck dissection versus observation in treating the N0 neck.

Bibliography

J.G. Armstrong, L.B. Harrison and R.H. Spiro= et al., Malignant tumors of major salivary gland origin: A matched pair analysis of the role of combined surgery and postoperative radiation therap= y, Arch Otolaryngol Head Neck Surg 116 (1990), pp. 290–293.

J.G. Armstrong, L.B. Harrison and H.T. Thale= r et al., The indications for elective treatment of the neck in cancer of the major salivary glands, Cancer 69 (1992), pp. 615–619.

Chen, AM et al.,Patterns of nodal rel= apse after surgery and postoperative radiation therapy for carcinomas of the maj= or and minor salivary glands: what is the role of elective neck irradiation?, = Int J Radiat Oncol Biol Phys. 2007 Mar 15;67(4):988-94.

R.A. Frankenthaler, R.M. Byers and M.A. Luna= et al., Predicting occult lymph node metastasis in parotid cancer, Arch Otolaryngol Head Neck Surg 119 (1993), pp. 517–520.

W.F. McGuirt, Management of occult metastatic disease from salivary gland neoplasms, Arch Otolaryngol Head Neck Surg 115 (1989), pp. 322–325.

J.E. Medina, Neck dissection in the treatmen= t of cancer of major salivary glands, Otolaryngol Clin North Am <= span style=3D'mso-bidi-font-weight:normal'>31 (1998), pp. 815–822.

C.A. North, D.J. Lee and S. Piantadosi et= al., Carcinoma of the major salivary glands treated by surgery or surgery plus postoperative radiotherapy, Int J Radiat Oncol Biol Phys 18 (1990), pp. 1319–1326.

E. Stennert, D. Kisner and M. Jungehuelsing = et al., High incidence of lymph node metastasis in major salivary gland cancer, Arch Otolaryngol Head Neck Surg 129 (2003), pp. 720–723.

P. Zbaren, J. Schupbach and M. Nuyens et = al., Elective neck dissection versus observation in primary parotid carcinoma, <= i>Otolaryngol Head Neck Surg 132<= /span> (2005), pp. 387–391.

<= /p>

<= /o:p>