Multidisciplinary Recommendations for Routine Follow-up of IDH‑Mutant Glioma in 2025: Adapting Clinical Practice to the Molecular Era

Abstract Little attention is given how to best follow patients with an IDH mutant grade 2 or grade 3 glioma over time. Most of these tumors are slowly growing, they usually respond to various therapies but adverse events of treatment can have an impact on the daily functioning of patients. Follow-up of these patients requires a schedule that fits in with this: monitoring the tumor for response to treatment and to timely identify progression in relation to the clinical course that may be expected, while avoiding unnecessary frequent follow-up that will not improve overall outcome. This paper provides recommendation for that. Grade 2 and most 3 IDH mutant diffuse glioma are slow growing tumors, for which however no curative treatment is available. Although surgery as extensive as possible improves outcome, for virtually all patients at some point in time further treatment is necessary. Treatment with radiotherapy and chemotherapy is very effective in controlling tumor growth in most patients, but has side effects. Therefore, in many patients these are postponed and a post-operative ´watch and wait’ observational strategy is followed. With the approval of IDH inhibitors another effective strategy has emerged allowing further delay of treatment with radiotherapy and chemotherapy. This underscores the need for guidance how to best follow these patients during their subsequent phases of treatment, but most guidelines give only minimal recommendations for follow-up. Follow-up should not be limited to imaging only, but should also routinely assess seizures and cognition of patients. Follow-up intervals should be based on the risk of progression, allowing longer intervals for patients with oligodendroglioma, for more definitively treated patients and for patients with longer lasting disease stabilization. Evidence justifying a more intensive follow-up of patients on IDH inhibitors than for patients on a 'watch and wait’ strategy is lacking. Assessing a growth trajectory over time and routine 2D or 3D tumor assessment will allow identification of early changes in growth rate. This manuscript provides guidance for optimal follow-up of these patients with perspectives from all involved disciplines, as indeed the follow-up of these patients needs to be truly multidisciplinary, at every step along the pathway of these patients.