Salivary gland cancer (SGC) is one type of head and neck cancer, accounting for about 5% of all head and neck tumors and less than 0.5% of all cancers, making it relatively rare. SGC originates from the salivary glands and can involve the three major salivary glands (parotid, submandibular, and sublingual glands) as well as the minor salivary glands distributed throughout the oral cavity. For early to mid-stage SGC, surgery ± radiotherapy is the main treatment; for recurrent or metastatic (R/M) SGC, palliative treatment is required, symptomatic or rapidly progressive disease should take systemic therapy into account. R/M SGC is highly heterogeneous, however, high-quality evidence-based evidence related to drug treatment is still insufficient. Individualized drug treatment needs to determine the specific treatment plan according to the characteristics of the patient and the tumor. In addition to NGS sequencing, high-throughput models for in vitro drug sensitive tests are an effective means to improve clinical efficacy.

Organoids are in vitro cultured micro-organs with 3D structures, capable of spontaneous self-renewal, self-organization, and differentiation to form complex structures similar to real tissues, partially simulating the physiological functions of the source tissue or organ. Compared with other in vitro and in vivo models such as cell lines and patient-derived xenograft models, organoid models have unique advantages: they can more vividly retain the phenotypic, genetic, and functional characteristics of the original tissue, and have a short modeling cycle, high cost-performance ratio, and can achieve high throughput drug sensitive test. In 2018, a study showed that ex vivo drug sensitivity testing based on gastrointestinal tumor organoids has a very high predictive value for clinical efficacy, with a sensitivity of 100%, specificity of 93%, and positive and negative predictive values of 88% and 100%, respectively. In addition, cancer organoids have been developed from many other cancer types and its feasibility in guiding precision medicine is investigated. The aim of present study is to evaluate the consistency of drug efficacy between the clinical systemic treatment and drug sensitive test based on patient-derived organoid in R/M SGC patients. A prospective and multicenter observational study is planned to increase the generalizability and reliability of research conclusion.

The patients with R/M SGC would receive drug treatment according to the clinical guideline or doctor's experience, at the same time, tumor biopsy samples would be collected to establish PDO for drug sensitive test. Fifteen different drug regimens sensitive test would be performed, including the actual drug regimens that the patients clinically receive, and the corresponding ex vivo tumor inhibition rate would be recorded. After the patients received the clinical treatment, they would be followed up to collect the objective response rate (ORR), disease control rate (DCR), progression-free survival time (PFS), and overall survival time (OS). Finally, the consistency of drug efficacy would be evaluated between clinical systemic treatment and drug sensitive test based on patient-derived organoid.