Given the rarity of salivary gland malignancies—neoplasms that account for less than 1% to 5% of all head and neck cancers—limited evidence exists to support informed treatment guidance. The overall variability in the biologic behaviors of these neoplasms has further complicated clinical management.
A new ASCO guideline provides the first evidence-based recommendations for the management of salivary gland malignancies that has been developed by a multidisciplinary expert panel.1 Specifically, the guideline offers recommendations on preoperative evaluation, diagnostic and therapeutic surgical procedures, radiotherapy, systemic therapy, follow-up evaluations, and recurrent metastatic disease. In contrast, other available resources cover broader recommendations for all head and neck cancers, providing only brief recommendations for salivary gland cancer.
“Without a clear set of guidelines, it is certainly possible patients were receiving inappropriate treatment, either undertreatment or overtreatment,” said Jessica Geiger, MD, of the Cleveland Clinic and Guideline Co-Chair. “Hopefully, with this guideline, providers can more clearly navigate through a patient’s disease and provide a more standard therapy plan.”
Jessica Geiger, MD
Patrick Ha, MD
Guideline Co-Chair Patrick Ha, MD, of the University of California San Francisco Health, added that prior to the new guidance, understanding the complexity of care of patients with salivary gland malignancies may not have been fully appreciated.
“Because salivary gland malignancy is a rare set of cancers, I believe that providing a platform for all practitioners to understand the workup and basic management is paramount,” Dr. Ha said. “Experts and those with access to multidisciplinary teams can also benefit from some elements of these guidelines. By using best practices, I do think that the outcomes can improve for patients.”
Preoperative Evaluation Recommendations
The Expert Panel recommends tissue biopsy, such as fine-needle aspiration biopsy or core-needle biopsy, to help differentiate salivary gland cancers from nonmalignant salivary lesions. The guideline states providers can use core-needle biopsy if fine-needle aspiration biopsy proves inadequate. Pathologists may also perform ancillary testing, in the form of molecular or immunohistochemical studies, on core-needle biopsies and fine-needle aspiration biopsies to support diagnosis and identify risk of malignancy.
“From a surgical standpoint, I think that the need for tissue biopsy preoperatively to help guide accurate surgery and discussion with the patient is essential,” Dr. Ha said. “These biopsies can also undergo deeper molecular or immunohistochemical studies to more fully characterize the tumor.” Dr. Ha added that subsequent decisions about the extent of resection, nodal dissection, or facial nerve management all depend on the histology.
Several treatment recommendations are made in the new guideline that involve the use of systemic therapy for salivary gland malignancies. “From a medical oncology standpoint, reviewing the data for systemic therapy is important in both the adjuvant and recurrent/metastatic settings,” Dr. Geiger said. “The overall paucity of evidence in this realm of treatment really highlights the need for more clinical trials to address with confidence areas we are lacking strong definitive, evidence-based recommendations.”
The expert panel recommends against the addition of concurrent chemotherapy in patients with salivary gland malignancies who are undergoing adjuvant radiotherapy, at least outside the confines of a clinical trial. The same recommendation is applied for patients undergoing radiotherapy for inoperable salivary gland cancer. The guideline also recommends against offering adjuvant endocrine or targeted therapy outside of a clinical trial in patients with salivary gland tumors expressing androgen receptor and/or HER2/Neu.
The guideline recommends targeted therapy based on tumor molecular alterations in patients with nonadenoid cystic salivary gland cancer who are candidates for systemic therapy. Molecular alterations include those such as AR, HER2, and NTRK. In particular, targeted therapy could be offered to these patients if a clinical trial is not available. The expert panel added that there have been no randomized trials that have yet compared survival outcomes between different targeted systematic therapies in patients with salivary gland cancer. Despite this lack of data, pooled analyses of early-stage trials suggest molecular targeted therapies are associated with relatively high objective response rates.
“Although there are not many randomized trials for adjuvant therapy or treatment of metastatic disease, there have been advances in molecular testing and characterization,” Dr. Geiger said. “This testing has led to the genesis of newer rational trial design and, at least for secretory carcinoma, a very molecularly targeted drug against NTRK.”
“I’m excited by the recommendation wherein the use of molecular testing and looking for targetable alterations is now possible,” Dr. Ha said. “We know that the different tumors and cancers behave differently and have different molecular backgrounds.” He noted that the customization of treatment based on known differences “should get us further along in terms of response” and hopefully assist in the development of more targeted approaches with fewer side effects.
1. Geiger JL, Ismaila N, Beadle B, et al: Management of salivary gland malignancy: ASCO guideline. J Clin Oncol 39:1909-1941, 2021.
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