Dormancy in IDH-mutant gliomas: New insights into saltatory growth

Breakthrough findings presented at AAN 2026 suggest periods of dormancy may be common in IDH-mutant gliomas, with implications for surveillance and treatment timing

At the American Academy of Neurology 2026 Annual Meeting, Dr Jigisha Thakkar presented data from her abstract ‘Dormancy in IDH-mutant Gliomas: A Retrospective 2D and 3D Analysis Before and After Resection‘. Her study investigated patterns of dormancy in IDH-mutant gliomas, challenging long-standing assumptions of continuous tumor growth and suggesting that some patients may benefit from more individualized surveillance and treatment strategies. While these tumors are traditionally thought to grow in a steady, linear fashion, clinical observations suggest they may instead follow a saltatory pattern, alternating between periods of growth and prolonged dormancy. Understanding these patterns could help refine surveillance approaches and reduce unnecessary treatment-related toxicity. In this Q&A, Dr Thakkar discusses how intermittent dormancy in IDH-mutant gliomas may influence clinical decision-making, from MRI surveillance intervals to the timing of therapeutic intervention.

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What gap in our understanding of IDH-mutant gliomas prompted this study, and how does the concept of saltatory growth challenge existing assumptions of continuous tumor progression?

Current models of IDH-mutant glioma behavior largely assume steady, continuous growth, which often drives decisions around early intervention and treatment escalation. In clinical practice, however, we observed that some tumors appeared to remain stable for prolonged periods before growing again, suggesting a saltatory rather than linear growth pattern. Recognizing these dormant phases is important because it may allow clinicians to safely delay treatment in select patients, reducing exposure to the neurocognitive and systemic toxicities associated with surgery, radiation, or chemotherapy while still maintaining close surveillance and appropriate long-term disease management.

Can you briefly outline your study design, including how patients were selected and how you defined and measured tumor dormancy over time?

We performed a retrospective analysis of adults with pathologically confirmed IDH-mutant gliomas from a single neuro-oncology practice between 2019 and 2025. Eligible patients had at least one year of serial MRI surveillance either before or after surgical resection and had not received adjuvant therapy. Tumor growth was assessed using serial two-dimensional measurements on T2-FLAIR MRI sequences. We defined dormancy as less than 2 mm of growth over a minimum one-year interval. To strengthen our findings, we also performed volumetric analyses using 3D imaging software in collaboration with an experienced neuroradiologist.

What were the key findings regarding dormancy patterns before surgical resection, particularly across astrocytomas and oligodendrogliomas?

We identified evidence of dormancy in both the pre-resection and post-resection settings. Among patients monitored before surgery, astrocytomas demonstrated prolonged dormant intervals lasting approximately 15 months and, in one case, up to 120 months. In contrast, the oligodendroglioma case in this cohort showed more continuous growth without a clearly defined dormant phase. Although the sample size was limited, these findings suggest that growth behavior in IDH-mutant gliomas may be more heterogeneous than previously appreciated and that prolonged radiographic stability can occur, particularly in certain astrocytoma cases.

What did you observe about tumor behavior after resection, including the frequency and duration of dormancy and differences between tumor subtypes?

After surgical resection, 80% of patients experienced at least one period of radiographic dormancy. Oligodendrogliomas appeared to exhibit the most prolonged stable phases, with a median dormancy duration exceeding 36 months. Astrocytomas showed greater variability, with some tumors remaining dormant for extended periods while others demonstrated more continuous progression. These findings support the idea that saltatory growth is common after resection and may differ by tumor subtype. Understanding these subtype-specific patterns could help clinicians better predict disease behavior and tailor surveillance intervals and treatment timing more appropriately.

How might these findings influence clinical decision-making, particularly around surveillance strategies and the timing of adjuvant therapy in IDH-mutant gliomas?

Our findings suggest that intermittent dormancy may be a common feature of IDH-mutant gliomas, challenging the assumption that all tumors grow continuously over time. This has important implications for clinical management, particularly when deciding when to initiate adjuvant therapy. In carefully selected patients with indolent disease and prolonged radiographic stability, continued surveillance may be a reasonable approach that helps defer treatment-related toxicity without compromising outcomes. These results also support current Society for Neuro-Oncology (SNO) and European Association of Neuro-Oncology (EANO) recommendations emphasizing individualized management strategies and highlight the need to reconsider conventional growth benchmarks when assessing tumor progression.