PRIMARY OBJECTIVE:~I. To determine if trastuzumab emtansine (ado-trastuzumab emtansine [T-DM1]) shows better progression-free survival (PFS) when compared to docetaxel plus trastuzumab (TH) in recurrent and/or metastatic (R/M) HER2-positive salivary gland cancer (SGC) patients who have not previously received HER2 therapy for unresectable or recurrent and/or metastatic disease, as determined by local assessment.~SECONDARY OBJECTIVES:~I. To compare the overall response rate (ORR) by Response Evaluation Criteria in Solid Tumors (RECIST) version (v)1.1 criteria between arms.~II. To compare overall survival (OS) between arms. III. To compare toxicity using Common Terminology Criteria for Adverse Events (CTCAE) v5.0 criteria between arms.~IV. To assess patient-reported toxicity, as measured by the patient reported outcome (PRO)-CTCAE, between arms, and explore patient-reported symptomatic adverse events (AEs) for tolerability of each treatment arm as measured by the PRO-CTCAE.~EXPLORATORY OBJECTIVES:~I. To assess the ORR in patients who receive crossover treatment to T-DM1/TH following disease progression on the TH arm/T-DM1 arm.~II. To collect blood and tissue specimens for future translational science studies to examine how tumor genetics, HER2 signaling output/expression, and HER2 tumoral heterogeneity impact TH and T-DM1 efficacy.~OUTLINE: Patients are randomized to 1 of 2 arms.~ARM I: Patients receive docetaxel intravenously (IV) over 60 minutes on day 1 of each cycle. Treatment repeats every 21 days for up to 6 cycles in the absence of disease progression or unacceptable toxicity. Patients also receive trastuzumab IV over 90 minutes on day 1 of each cycle. Cycles repeat every 21 days in the absence of disease progression or unacceptable toxicity.~ARM II: Patients receive trastuzumab emtansine IV over 90 minutes on day 1 of each cycle. Cycles repeat every 21 days in the absence of disease progression or unacceptable toxicity.~After completion of study treatment, patients are followed up every 3 months for 2 years and then every 6 months for 3 years.
This phase II trial tests whether ado-trastuzumab emtansine works to shrink tumors in patients with HER2-positive salivary gland cancer that has come back (recurrent), spread to other places in the body (metastatic), or cannot be removed by surgery (unresectable). Trastuzumab emtansine is a monoclonal antibody, called trastuzumab, linked to a chemotherapy drug called emtansine. Trastuzumab attaches to HER2 positive cancer cells in a targeted way and delivers emtansine to kill them. Trastuzumab emtansine may work better compared to usual treatment of chemotherapy with docetaxel and trastuzumab in treating patients with salivary gland cancer.