e20630 Background: Although various prognostic factors have been proposed to predict survival in terminally ill cancer patients, accurate prognostication is still a challenging task for oncologists. The objective of this study was to evaluate whether the time interval between diagnosis of advanced cancer and cessation of active anti-cancer treatment (ATP; active treatment period) can predict survival in terminally ill cancer patients. Methods: We prospectively evaluated 79 patients with advanced (recurrent or metastatic) cancer who were determined as terminal stage, namely cessation of active anti-cancer treatment and transition to palliative care, by attending oncologists. ATP and other known prognostic factors including clinical symptoms and signs, performance status, laboratory tests, and clinical prediction of survival (CPS) were analyzed. Results: Of the 79 patients, 46 were male (58%) and 33 were female (42%) with a median age of 60 years (range, 21–82). Median overall survival after being diagnosed with advanced cancer was 11.6 months (95% confidence interval (CI), 8.02–15.18), and survival after being determined as terminal stage was 1.9 months (95% CI, 1.38–2.42). According to 3 ATP categories (< 3months, 3–12 months, and >12 months), terminal stage survival were 1.0 month, 1.8 months, and 3.6 months, respectively (p=0.002). On multivariate analysis, short ATP, non-colorectal cancer, fatigue, and Karnofsky performance status less than 50 were significantly associated with a poor prognosis. Conclusions: Our study suggests that ATP is an independent prognostic factor for survival in terminally ill cancer patients who cannot receive active anti-cancer treatment anymore. Future prognostic models should include ATP as a prognostic variable. No significant financial relationships to disclose.