A tissue-removing catheter includes a cutter having an axial cavity and an opening extending from the axial cavity through the cutter to allow tissue removed from the body lumen by the annular cutting edge to pass proximally through the opening. A cutter driveshaft defines a tissue-transport passage extending longitudinally therein and in communication with the axial cavity of the cutter. A screw blade extends longitudinally within the tissue-transport passage and includes an external helical thread for transporting removed tissue proximally within the tissue-transport passage as the screw blade rotates about its axis. The cutter driveshaft having a distal end portion operatively coupled to the cutter for driving rotation of the cutter.