Objectives: Glioblastoma(GBM) is one of the worst cancers in terms of prognosis.Standard therapy consists of resection with concomitant chemoradiotherapy.Resistance to nimustine hydrochloride(ACNU),an alkylating agent,has been linked to methylguanine DNA methyltransferase(MGMT).Daily administration of procarbazine(PCZ) has been reported to decrease MGMT activity.This study investigated the efficacy of ACNU + PCZ compared to ACNU alone for GBM and anaplastic astrocytoma(AA).Methods: Patients(20-69 years) who had newly diagnosed AA and GBM were randomly assigned to receive radiotherapy with ACNU alone or with ACNU + PCZ.The primary endpoint was overall survival(OS).This was designed as a phase Ⅱ/Ⅲ trial with a total sample size of 310 patients and was registered as UMIN-CTR C000000108.Results: After 111 patients from 19 centers in Japan were enrolled,this study was terminated early because temozolomide was newly approved in Japan.The median OS and median progression-free survival(PFS) with ACNU alone(n = 55) or ACNU + PCZ(n = 56) in the intention-to-treat population were 27.4 and 22.4 months(P = 0.75),and 8.6 and 6.9 months,respectively.The median OS and median PFS of the GBM subgroup treated with ACNU alone(n = 40) or ACNU + PCZ(n = 41) were 19.0 and 19.5 months,and 6.2 and 6.3 months,respectively.Grade 3/4 hematologic adverse events occurred in more than 40% of patients in both arms,and 27% of patients discontinued treatment because of adverse events.Conclusions: The addition of PCZ to ACNU was not beneficial,in comparison with ACNU alone,for patients with newly diagnosed AA and GBM. Objectives: Glioblastoma (GBM) is one of the worst cancers in terms of prognosis. Stardard therapy consists of resection with concomitant chemoradiotherapy. Resistance to nimustine hydrochloride (ACNU), an alkylating agent, has been linked to methylguanine DNA methyltransferase (MGMT) .Daily administration of procarbazine (PCZ) has been reported to decrease MGMT activity. This study investigated the efficacy of ACNU + PCZ compared to ACNU alone for GBM and anaplastic astrocytoma (AA). Methods: Patients (20-69 years) who had newly diagnosed AA and GBM were randomly assigned to receive radiotherapy with ACNU alone or with ACNU + PCZ. The primary endpoint was overall survival (OS). This was designed as a phase II / III trial with a total sample size of 310 patients and was registered as UMIN -CTR C000000108.Results: After 111 patients from 19 centers in Japan were enrolled, this study was terminated early because temozolomide was newly approved in Japan.The median OS and median progression-free survival (PFS ) with ACNU alone (n = 55) or ACNU + PCZ (n = 56) in the intention-to-treat population were 27.4 and 22.4 months (P = 0.75), and 8.6 and 6.9 months, respectively.The median OS and median PFS of the GBM subgroup treated with ACNU alone (n = 40) or ACNU + PCZ (n = 41) were 19.0 and 19.5 months, and 6.2 and 6.3 months, respectively. Grade 3/4 hematologic reverse events occurred in more than 40% of patients in both arms, and 27% of patients discontinued treatment because of adverse events. Conclusions: The addition of PCZ to ACNU was not beneficial, in comparison with ACNU alone, for patients with newly diagnosed AA and GBM.