The Effectiveness of Salvage Treatments for Recurrent Lesions of Oligodendrogliomas Previously Treated with Upfront Chemotherapy

Background: We previously reported a favorable outcome in a case series of patients with oligodendrogliomas treated with upfront chemotherapy; however, their progression-free survival (PFS) was relatively short considering their long-term overall survival (OS). This suggests that salvage treatments after progression were effective. However, the clinical impact of salvage treatments on outcomes of patients with recurrent oligodendrogliomas has not been precisely investigated. Methods: Our case series included 28 patients with newly diagnosed isocitrate dehydrogenase–mutant and 1p/19q-codeleted oligodendroglial tumors treated with upfront procarbazine, nimustine, and vincristine. Clinical outcomes and patterns of recurrence were reviewed retrospectively. Results: The median follow-up period of enrolled patients was 90.2 months. Disease progression occurred in 15 patients (53.6%), whereas the cancer appeared as local relapse alone in 14 (93.3%) patients. Salvage treatments were performed for all local relapses; thereafter, most of the subsequent progressions also appeared as resectable local relapses. The 5-year PFS and OS rates from the first progression were 30.3% and 92.9%, respectively. These relatively short PFS and favorable OS indicated the effectiveness of salvage treatment even after multiple progression. Thus far, 9 (60%) of 15 patients are deterioration-free with locally controlled lesions or complete remission; however, clinical deterioration was observed in 6 patients, and 4 of them experienced dissemination. Conclusions: In isocitrate dehydrogenase–mutant and 1p/19q-codeleted oligodendrogliomas, most of the tumors that demonstrated early progression appeared as local, nonlethal lesions, which have been well-controlled by salvage treatments. A precise diagnosis of oligodendrogliomas using molecular parameters is crucial to receive the best benefit from salvage treatment.