What Is the Utility of Tumor Growth Rate in Glioma Treatment?

Presented at the 2026 American Society of Clinical Oncology Annual Meeting, updated results with extended follow-up from the phase 3 INDIGO trial (NCT04164901) showed that vorasidenib (Voranigo) demonstrated a median progression-free survival of 44.1 months (95% CI, 27.7-not evaluable) in patients with grade 2 IDH1/2-mutant glioma. Vorasidenib also delayed the need for subsequent treatment.

In the analysis, it was also found that the number of patients with tumor shrinkage and the depth of response to vorasidenib improved over time. The overall response rate increased from 10.7% (95% CI, 6.5%-16.4%) in September 2022 to 20.8% (95% CI, 15.0%-27.8%) in January 2025.

CancerNetwork^® spoke with Timothy F. Cloughesy, MD, the presenting study author, at the conference, particularly about how oncologists and neuro-oncologists should incorporate tumor growth rate into their assessment of treatment outcomes.

He affirmed that tumor growth rate did precisely give information regarding progression, which is different from what was observed with placebo. However, the evaluation is not standard and it is unlikely the everyday oncologist or neuro-oncologist will have the availability to investigate tumor growth rates. Currently, they have more utility in drug development and discovering combinational approaches. 

Cloughesy is professor and codirector of the UCLA Brain Tumor Center, director of the UCLA Neuro-Oncology Program, and codirector of the Henry F. Singleton Brain Cancer Research Program.

Transcript:

CancerNetwork: How should neuro-oncologists incorporate tumor growth rate into how they assess early vorasidenib treatment success on MRI vs relying strictly on standard RECIST or RANO [Response Assessment in Neuro-Oncology] criteria?

Cloughesy: The study was run based upon the RANO criteria, which is a bidirectional measurement, so all of the response determining progression…was based on [RANO]. We are also doing evaluations with volume, and it appears that volume is a little more precise at giving us this information. It is interesting that, in some of the patients, we were able to get data before coming on the study; that meant that we could do a trajectory of growth rates coming into the study and then what the impact is on the growth rate after. It's very clear that there's a big difference when compared with placebo, an alteration in this growth rate. It emphasizes more the impact of this drug and what it's having.

This is not a common evaluation, though. This is not something that everyday oncologists would have, and many neuro-oncologists don't have the availability of looking at these tumor growth rates. These tumor growth rates are going to turn into a tool that could be used for drug development and for better understanding, maybe how to consider combination approaches and the contribution of effect, by looking at the degree at which the growth rate has been altered. But it's not going to be something that's going to be entering into clinical practice, although the volumetric measurements that seem to be a little more precise might be something that is.

Reference

Cloughesy TF, van Den Bent MJ, Blumenthal DT, et al. A global, randomized, double-blinded, phase 3 trial of vorasidenib vs placebo in patients with grade 2 glioma with an IDH1/2 mutation (INDIGO): updated efficacy and safety. J Clin Oncol. 2026;44(suppl 16):2010. doi:10.1200/JCO.2026.44.16_suppl.2010