353 Background: The prognostic impact of number of lines of prior chemotherapy and prior perioperative chemotherapy on survival results in salvage trials for advanced UC is unknown. Methods: We pooled 10 prospective phase II trials of salvage therapy for advanced UC with data on the number of prior lines of therapy in addition to known prognostic factors: TFPC (time from prior chemotherapy), Hb (hemoglobin), PS (performance status), and LM (liver metastasis) status. Cox proportional hazards regression was used to evaluate the association of number of prior lines with overall survival (OS) and progression-free survival (PFS). Trial was included as a stratification factor. Sub-analysis examined the impact of prior perioperative chemotherapy. Results: Of 731 pts, data for all factors was available for 711. The overall median PFS and OS were 2.7 and 6.8 months, respectively. Trials evaluated vinflunine (N=151), docetaxel +/- vandetanib (N=147), paclitaxel-gemcitabine (N=83), sunitinib (N=77), nab-paclitaxel (...