Background: Salivary gland carcinoma is a rare type of cancer, and when metastasized is associated with poor prognosis. Response rates to standard chemotherapy are less (15-30%) and usually short-lived. Salivary gland tumors expressing HER2/neu have lately been recognized. We describe 2 cases of ERBB2 amplification identified by NGS testing with response to Anti Her-2 therapy.
Case 1 : A 69-year-old male veteran was originally diagnosed with a left parotid gland carcinoma at pleomorphic adenoma in September 2015. Patient underwent surgery with a left parotidectomy 4 out of 85 lymph nodes were positive for metastasis (T3, N2b, Mx, G3, Stage IVA disease). Patient was offered adjuvant chemo/XRT but was lost to follow-up. In October 2016, patient presented with recurrent left parotid gland swelling staging workup revealed diffuse metastatic disease to liver and bone. Patient had a palliative resection of the left parotid mass tumor was consistent with carcinoma and was offered palliative chemotherapy with carbo platinum and Taxol. After 4 cycles of chemotherapy repeat PET CT scan revealed progression of disease with new sternal, T3 vertebral, right sacral and numerous liver and upper abdominal lymph nodes. Next generation sequencing (NGS) by Foundation One revealed ERBB2/HER2 mutation. Patient was started on second-line palliative chemotherapy utilizing docetaxel and Herceptin every 3 weeks. After 3 cycles restaging PET CT scan showed good partial response in bone and stable disease in the liver.
Case 2: A 73-year-old male presented on 4/16 with rapidly enlarging recurrent mass and bone pain one year after right radical neck dissection followed by adjuvant XRT. Pathology demonstrated salivary gland adenocarcinoma. PET/CT: extensive axial and appendicular skeletal metastasis with widespread bony pain. NGS testing of the original pathology with Foundation One revealed ERBB2 amplification as well as alteration of PTEN and TP53. Patient was offered Carboplatin + Herceptin which he received and tolerated well. Pain resolved after 1st cycle. Metabolic PR by PET/CT was noted after 4 cycles.
Conclusions: Adding trastuzumab to chemotherapy in patients with Her2/neu-positive metastatic salivary gland carcinoma gave promising results. Our institutional experience matches with few other case reports/series published to date. Validating this results with a randomized study would be a challenge, given the rarity of this disease.
