Long-term outcome of nimustine (ACNU)-based chemotherapy for oligodendroglioma

Background Combination chemotherapy of procarbazine, lomustine (CCNU), and vincristine (PCV), a standard treatment for oligodendroglioma, is associated with frequent adverse events. In Japan, only nimustine (ACNU), an analog of CCNU, is approved. This study aimed to evaluate the long-term outcomes of ACNU-based chemotherapy after maximal safe resection with deferred radiation therapy (RT) for oligodendrogliomas. Methods This retrospective study included 50 patients diagnosed with IDH-mutant 1p/19q-codeleted oligodendroglioma of grades 2 (n = 27) or 3 (n = 23) between 2002 and 2022. Progression-free survival (PFS), overall survival (OS), and time to decline in performance status (deterioration-free survival [DFS]) were analyzed using the Kaplan–Meier method. Results Postoperative chemotherapy was administered to 94% of patients (procarbazine, ACNU, and vincristine [PAV], n = 24; ACNU, n = 22; temozolomide [TMZ], n = 1; excluded). Median follow-ups were 142.9 and 50.6 months for PAV and ACNU groups, respectively. Ten-year PFS rates were 54.2% and 30.0% for grades 2 and 3 tumors, respectively, (p = 0.0870), and 10-year OS rates were 91.5% and 78.8% for grades 2 and 3, respectively (p = 0.5098), with comparable DFS (p = 0.6922). Comparing regimens, the 10-year OS rate was 82.3% for PAV, while all patients in the ACNU group remained alive. Five-year PFS were almost identical: 58.9% (PAV) vs. 56.8% (ACNU), p = 0.9996. Treatment completion rates were 75% and 91% for PAV and ACNU, respectively. Conclusions ACNU monotherapy has a similar efficacy to PAV and tolerability to TMZ, suggesting that it is the most favorable chemotherapeutic option currently available in Japan, considering its risk-benefit profile.