Ramucirumab in combination with dacarbazine in patients with progressive well-differentiated metastatic pancreatic neuroendocrine tumors (RamuNET): study protocol for a multicenter single-arm trial - Krug, Sebastian; Kegel, Thomas; Gress, Thomas Mathias; Rinke, Anja; Apostolidis, Leonidas; Jann, Henning; König, Alexander; Hörsch, Dieter; Schrader, Jörg; Ettrich, Thomas J.; Richter, Michael; Steighardt, Jörg; et al. (BMC cancer, 2021)