BACKGROUND: Recent clinical trials have shown that patients with metastatic castration-sensitive prostate cancer in real-world settings have different overall survival (OS) rates after stratifying for tumor burden or visceral metastasis. However, some patients with a low tumor burden and without visceral metastasis still have a poor survival. Androgen receptor signaling is still a main therapeutic target of prostate cancer treatment even after the achievement of castration resistance. In this regard, we hypothesized that time to castration resistance can be a prognostic factor of metastatic castration-sensitive prostate cancer even after achieving castration resistance. The current study aimed to assess the novel prognostic factors, particularly time to castration resistance, of prostate cancer in patients at a real-world single institution. METHODS: The data of 261 patients who were newly diagnosed with metastatic castration-sensitive prostate cancer from January 2007 to December 2023 were retrospectively analyzed. RESULTS: The median OS was 60.7 months, and the median time to castration resistance was 13.1 months. Among 261 patients, 158 developed castration-resistant prostate cancer. A shorter time to castration resistance, the presence of distant lymph node metastasis, ISUP grade group 5, and older age were associated with a shorter OS in patients who developed castration-resistant prostate cancer. A shorter time to castration resistance was significantly associated with a shorter OS regardless of the tumor burden. Further, it was associated with a shorter OS even after the achievement of castration resistance. CONCLUSIONS: The study results support the presence of persistent androgen receptor signaling even after achieving castration resistance in prostate cancer, and time to castration resistance can be a biomarker for the activation of androgen receptor signaling regardless of tumor burden.