Grade 2 IDH-Mutant Glioma: Vorasidenib Now or Definitive Chemoradiation First
A subtotally resected grade 2 glioma sits inside the eligibility window for a new, non-genotoxic oral therapy — and inside a family-planning window that makes the genotoxic alternative a harder sell than the trial data alone would suggest.
Daniel R., a 34-year-old man, teaches middle-school science and coaches the school's cross-country team, and had never had a seizure in his life before one interrupted a faculty meeting eighteen months ago — a brief episode of right-hand jerking and word arrest that his colleagues described more clearly than he could himself. Imaging showed a non-enhancing left frontal lesion abutting the motor strip, and he underwent an awake craniotomy four months later; the surgeon reached roughly 80 percent of the visible tumor before intraoperative mapping over the hand-motor area forced her to stop, leaving a small residual rind of non-enhancing tissue along the resection margin — a subtotal resection, not the gross-total one everyone had hoped for going in. Pathology returned IDH1-mutant, 1p/19q non-codeleted astrocytoma, WHO grade 2. He has been seizure-free since on levetiracetam, is otherwise entirely healthy, and returned to full-time teaching within two months of surgery.
Fourteen months out, his MRI is stable — no new enhancement, no growth of the residual non-enhancing tissue — and his Karnofsky score is 90, functionally back to where he started. He and his wife have also been direct with the team about wanting to start a family in the next two or three years, a detail that turns out to matter as much as any scan. INDIGO, the trial that established vorasidenib's benefit in exactly this setting, enrolled patients with residual or recurrent grade 2, IDH-mutant, non-enhancing glioma one to five years from their most recent surgery, KPS above 80, and no immediate need for chemotherapy or radiation in the treating physician's judgment — Daniel matches that population on every count. But his subtotal resection also places him squarely in the high-risk stratum RTOG 9802 used to select patients for radiation plus PCV chemotherapy, a trial whose survival advantage is real and mature, not just delayed progression. What sits between those two proven results is a drug he has not yet been offered: vorasidenib extends the time before either PCV or radiation becomes necessary, without the alkylating agents' mutagenic and gonadotoxic profile — a difference that matters specifically to a man who wants his fertility intact when that conversation happens again.
Tumor board, fourteen months after surgery
He clears INDIGO's own eligibility bar almost to the letter — surgery inside the one-to-five-year window, KPS well above 80, non-enhancing residual disease, and no immediate need for chemotherapy or radiation by any reasonable read of his scan. Vorasidenib delayed the time to next intervention substantially against placebo in exactly this population, and it does that without asking him to accept an alkylating regimen's toxicity today for a tumor that isn't demanding it today.
I want to be precise about what this buys him: time before the next decision, not a substitute for ever making it. If his disease progresses or the residual tissue starts enhancing, we're back to this same table.
I'd frame the comparison differently. RTOG 9802 didn't test time-to-progression — it tested overall survival, in a population defined by exactly the feature he has: age under 40 doesn't exempt a patient once resection is subtotal, and that trial's radiation-plus-PCV arm produced a durable survival advantage over radiation alone that has now matured over more than a decade of follow-up. Vorasidenib's own trial hasn't reported overall survival yet.
I don't dispute that vorasidenib delays the next intervention — the INDIGO data are real. What I'd push back on is treating that delay as equivalent to the survival benefit RTOG 9802 actually measured. Those are different endpoints, and for a high-risk-by-resection patient, the one with mature survival data is the one I'd be reluctant to defer indefinitely.
Both of you are arguing the trial data correctly, and I think the disagreement actually resolves once we name the variable neither trial was built around: he wants children in the next two to three years, and PCV's components aren't incidental to that. Procarbazine and the alkylating agent lomustine both carry documented, dose-related gonadotoxicity, and while vincristine's own gonadal risk is smaller, the regimen as a package is one we'd generally counsel fertility preservation before starting.
You're right that RTOG 9802's survival benefit is real and I'm not arguing to discard it — I'm arguing for sequencing, not substitution. Start vorasidenib now, during the window where his own disease trajectory allows it and his family-planning timeline actively prefers it, and revisit radiation plus PCV once either his scan changes or he and his wife have completed that decision. That's a genuinely different plan from 'vorasidenib instead of PCV forever.'
Agreed: start vorasidenib now, with MRI reassessment at three months and every three months thereafter, and an explicit referral to reproductive endocrinology this week for fertility preservation counseling regardless of which regimen he ultimately needs — a step that costs nothing against either pathway and forecloses nothing.
Not agreed, and stated plainly rather than smoothed over: whether vorasidenib is genuinely a bridge to eventual radiation and PCV, or whether a patient who tolerates it well and stays stable for years should ever be moved off it onto a regimen with proven survival benefit but real reproductive cost. The radiation oncologist wants that question revisited at the first sign of any change on imaging, not deferred indefinitely on the strength of a stable scan; the neuro-oncologist would let a genuinely stable, well-tolerated course run for years before reopening it. Both agreed to bring the question back explicitly at his one-year vorasidenib mark, whichever way his scans go.