Second-Line Treatment of HER2-Positive Salivary Gland Tumor: Ado-Trastuzumab Emtansine (T-DM1) after Progression on Trastuzumab

Patients with salivary duct cancer (SDC) and HER2 overexpression could receive trastuzumab in combination with chemotherapy for metastatic disease. No standard treatment exists for patients with HER2-positive metastatic SDC after progression. We report an excellent patient response to second-line treatment with T-DM1 after progression on paclitaxel plus trastuzumab. CASE REPORT: In June 2014, a 79-year-old male patient underwent right parotidectomy and ipsilateral radical neck dissection after the diagnosis of parotid carcinoma. Pathological staging demonstrated locally advanced disease with the involvement of 13 lymph nodes (levels I, II, III, and IV), with extracapsular extravasation. He underwent adjuvant radiotherapy ending in December 2014. A PET scan in March 2015 diagnosed recurrent and systemic disease, with bone lesions, neck lymph node involvement, and hepatic metastasis. The immunohistochemistry showed HER2 receptor overexpression (+3/+3). The patient received first-line trastuzumab plus paclitaxel beginning in April 2015. After 6 cycles, his response was confirmed by PET scan. In February 2016, he had symptoms of disease progression, and a PET scan revealed disease progression in the neck, bones, and liver. He started T-DM1 in April 2016. The neck skin lesions disappeared after 6 cycles, with low toxicity. PET scans performed every 3 months showed response in the liver and bone lesions. CONCLUSIONS: We report the case of a patient with SDC treated with T-DM1, with a very good response. Salivary carcinoma is a rare disease for which no randomized clinical trials are available. The maintenance of HER2 blockage might be important in this disease.