Salivary gland cancer (SGC): the next steps

Until recently, research in salivary gland cancer, which can be divided in 24 subtypes, was scarce. The results of palliative systemic treatments, i.e. chemotherapy, were disappointing in case of irresectable local, regional recurrence or distant metastases. Despite the rarity of the cancer, which has caused the low number of new systemic treatments being investigated in the past, new research has been initiated in 2009. Because salivary duct cancer (SDC) shows similarities with prostate cancer by expression of the androgen receptor in almost all patients (Slootweg and van Engen), studies with hormonal treatment, i.e. androgen deprivation therapy (ADT) in SDC AR+ patients were started. ADT appeared to be effective and we published a series of 10 patients (the largest series at that time) in the Journal of Clinical Oncology (J Clin Oncol 2011). Recently, an update in 35 patients was published (Head Neck 2018). Furthermore, the material of 175 SDC patients, diagnosed in the Netherlands, was collected, and the forthcoming patient characteristics were reviewed (Int J Cancer 2018). Tissue microarrays (TMAs) were made and used to study predictive and prognostic factors. Since 2016 also adjuvant ADT in SDC AR+ patients was studied and combined with data of Milan (Licitra and Locati; van Boxtel et al, submitted). In all patients with SDC we perform next generation sequencing (NGS) and in part of them WGS (in collaboration with the CPCT). Patients are offered personalized treatments based on this data (Oral Oncol 2017). Almost all patients with salivary gland cancer, especially SDC patients and all patients with metastases, are referred from the Dutch hospitals to our hospital. Therefore, together with patients a patient network was established in 2015. Together with the patient network, we currently discuss with healthcare insurances further centralization of care for patients with salivary gland cancer. Furthermore, in collaboration with pharmaceutical companies investigator-initiated studies were started, e.g. cabozantinib in c-met positive SGC patients. Also a PSMA imaging study in 25 patients with SGC was performed, which was sponsored by the Dutch network Salivary Gland Cancer and the Adenoid Cystic Carcinoma Research Foundation (ACCRF).
Recently, the SGC biobank started and of most SGCs organoids are made. Together with the tumor immunology laboratory the immune microenvironment of SGCs is investigated. The results of these studies lead to better care for SGC patients, which in turn leads to a prolonged survival in part of the patients with a good quality of life. Furthermore, the research in SGC attracts young talent (Boon and van Boxtel).