Pembrolizumab as a First Line Therapy in a Patient with Extensive Mucoepidermoid Salivary Gland Carcinoma: A Complete Clinical, Radiological And Pathological Response: A Very Specific Case

Background: The treatment options for patients with advanced Salivary Gland Cancers (SGCs) are limited. Results from recently published studies indicate a possible use for checkpoint inhibition in a subset of patients, but there are no established criteria for Programme Cell Death Ligand 1 (PD-L1) scoring in SGCs. The benefit of chemotherapies was reported to be minimal with a prognosis that remains poor in unresectable and high grade SGC.

Immunotherapies have shown remarkable success in various entities not limited to non-small cell lung cancer and malignant melanoma. Pembrolizumab, an anti-PD-1 antibody, has been proven to have strong anti-tumor activity in a variety of clinical studies.

Case Presentation: We report a unique case of advanced high grade mucoepidermoid carcinoma of the parotid salivary gland after Pembrolizumab treatment as a first line therapy.

Pembrolizumab treatment resulted in downstaging of the tumor which lead to its successful surgical resection with no facial nerve sacrifice and no serious side effects of the neoadjuvant treatment, and the final specimen pathology was free of tumor. A similar strategy that resulted in Complete Response (CR) radiologically and pathologically has never been mentioned before in these kind of tumors.

Conclusions: Pembrolizumab has demonstrated a promising antitumor activity in pretreated patients with high grade salivary gland mucoepidermoid carcinoma, and offered a clinically, radiological and pathological response with a meaningful therapeutic option. Further studies that move the treatment of Pembrolizumab to front-line are necessary. These studies should include the time and duration of the pharmacotherapy in relation to the needed time of surgery.