We exhibit our ongoing multicenter, prospective, single-arm, phase II trial of docetaxel plus ramucirumab with primary prophylactic pegylated-granulocyte-colony stimulating factor (PEG-G-CSF) support for chemotherapy-naive elderly patients with advanced non–small-cell lung cancer (NSCLC) (University Hospital Medical Information Network database: UMIN000030598). Docetaxel monotherapy is the Japanese standard of care for chemotherapy-naive elderly patients with advanced NSCLC. Docetaxel plus ramucirumab showed superior survival benefit over docetaxel monotherapy in the second-line setting for NSCLC. A Japanese phase II study comparing docetaxel plus ramucirumab and docetaxel monotherapy in the second-line setting showed febrile neutropenia (FN) incidence of approximately one-third in the docetaxel plus ramucirumab arm. Docetaxel plus ramucirumab could be a promising candidate for elderly patients with NSCLC, but such high FN incidence is a clinically critical concern. To overcome this problem, we adopt a routine primary prophylactic PEG-G-CSF with docetaxel plus ramucirumab therapy. We hypothesize that primary prophylactic PEG-G-CSF reduces FN and maximizes the efficacy of docetaxel plus ramucirumab in Japanese elderly patients with NSCLC. Intravenous docetaxel (60 mg/m2, day 1) plus ramucirumab (10 mg/kg, day 1) with subcutaneous PEG-G-CSF (3.6 mg, day 2) every 3 weeks is administered until progression. The primary endpoint is overall response rate (ORR). We decided the threshold ORR to be 20%, and the expected ORR 35%. Taking statistical points (α/β errors: 0.05/0.80) and ineligible patients into account, the sample size was set at 65. When the study results are promising, we will conduct a phase III trial to compare docetaxel plus ramucirumab with PEG-G-CSF support versus docetaxel monotherapy for chemotherapy-naive elderly patients with NSCLC.