Yuichiro Tada

Background Salivary duct carcinoma (SDC) is a high‐grade adenocarcinoma with a 5‐year survival rate of 40%. Although drug therapy has improved patients' prognosis, the impact of brain metastasis (BM) remains poorly understood. We aimed to retrospectively examine the incidence of BM in patients with SDC ( n = 464) and develop a tool to estimate their prognoses. Methods We retrospectively examined 464 patients with SDC enrolled in a multicenter study. We investigated the incidence of BM, overall survival (OS) rates, and factors affecting prognosis in patients with BM. We also developed an SDC‐graded prognostic assessment (GPA) score for disease prognostication. Results Sixty‐five (14%) patients had BM. The median OS (mOS) was 13.1 months. On univariate and multivariate analyses, factors such as Eastern Cooperative Oncology Group Performance Status >1, human epidermal growth factor receptor 2‐negative status, and locoregional uncontrolled disease were associated with poor OS. SDC‐GPA scores according to the prognostic factors were 0, 1, 2, and 3 points, and mOS estimates were 50.5, 16.1, 3.9, and 1.2 months, respectively ( p < 0.001). Conclusion The SDC‐GPA score emerged as a useful prognostication tool for patients with BM.