Salivary Duct Carcinoma (SDC)
Salivary Duct Carcinoma
Salivary Duct Carcinoma (SDC) is a rarer type of salivary gland cancer. One or two in a hundred salivary gland cancers are of this type.
SDC most commonly occurs in people in their 60’s or 70’s and is more common in men. It typically starts in the parotid salivary gland located between the ears and the jaw but can form in any of the major or minor salivary glands in the head, throat, and windpipe.
Unlike most salivary gland cancers, SDC is usually a faster growing (high-grade) type. It often metastasises (spreads from the original tumour site) early to nearby lymph nodes or further parts of the body (distant sites). This can make surgery and/or radiotherapy aimed at curing the cancer challenging, and the cancer has a high risk of returning later in life even with successful surgery.
All cancers have characteristics called markers, and in SDC these are very important to determining treatment options. Around three quarters of SDC are androgen receptor positive and two fifths of SDC overexpress the HER2 marker, with about a third overexpressing both. Both markers have drugs that can target them, and these are currently the best treatment options for widespread SDC.
Sometimes SDC expresses rarer markers that also have treatments available. Chemotherapy is more effective in SDC than other salivary gland cancers, but it is still quite resistant with only one in five people having a positive response in their cancer.