CATNON Trial Final Results Confirm Adjuvant Temozolomide Benefit in IDH-Mutant Anaplastic Glioma
Key Insights
The phase III CATNON trial's final analysis with 10.9 years median follow-up confirms that adjuvant temozolomide following radiotherapy significantly improves overall survival in patients with IDH-mutant anaplastic glioma (search).
Adjuvant temozolomide extended median overall survival to 12.5 years versus 6.0 years without adjuvant therapy in IDH (search)-mutant patients, while concurrent temozolomide during radiotherapy showed no significant benefit.
The survival benefit was restricted to IDH (search)-mutant tumors, with no improvement observed in IDH wild-type disease, establishing IDH status as the key determinant for treatment selection.
The final analysis of the landmark CATNON trial has definitively established the role of adjuvant temozolomide in treating patients with IDH-mutant anaplastic glioma (search), providing the most mature survival data in the modern molecular era with over a decade of follow-up. The results, published in The Lancet Oncology, demonstrate that radiotherapy followed by 12 cycles of adjuvant temozolomide significantly improves overall survival in this patient population.
Key Clinical Findings
The phase III study, conducted across 137 institutions in Australia, Europe, and North America, randomized 751 patients with newly diagnosed 1p/19q non-co-deleted anaplastic glioma (search) between December 2007 and September 2015. With a median follow-up of 10.9 years, the trial provides unprecedented long-term outcome data for this patient population.
In the intention-to-treat analysis, adjuvant temozolomide demonstrated a clear overall survival benefit compared to no adjuvant treatment (hazard ratio 0.65, 95% confidence interval 0.54-0.77). Conversely, concurrent temozolomide given during radiotherapy showed no significant benefit (HR 0.91, 95% CI 0.76-1.08).
IDH Status Drives Treatment Benefit
The most clinically significant finding emerged from the exploratory analysis of 444 patients with IDH (search)-mutant tumors. In this subgroup, adjuvant temozolomide produced a substantial improvement in overall survival, extending median survival to 12.5 years compared to 6.0 years without adjuvant therapy (HR 0.54, 95% CI 0.42-0.69).
Concurrent temozolomide in IDH (search)-mutant patients showed no statistically significant overall survival benefit, with median survival of 9.7 years versus 7.2 years without concurrent treatment (HR 0.81, 95% CI 0.63-1.04).
Critically, patients with IDH (search) wild-type tumors derived no benefit from either concurrent or adjuvant temozolomide, with the analysis showing no improvement in overall survival for either treatment approach. This finding underscores IDH status as the dominant determinant of treatment response.
Molecular Profiling Insights
The investigators conducted comprehensive molecular profiling in the IDH-mutant astrocytoma (search) subgroup, revealing several features associated with worse outcomes. Homozygous deletion of CDKN2A (search)/CDKN2B (search) was associated with particularly poor prognosis, with median overall survival of 3.0 years versus 9.6 years in patients without this alteration (HR 3.58).
PDGFRA (search) amplification similarly correlated with reduced survival, showing median overall survival of 3.1 years compared to 9.3 years without amplification (HR 3.51). Other adverse prognostic factors included PTEN (search) loss of heterozygosity (HR 2.38) and high total copy number variation load (HR 1.60).
Importantly, none of these molecular features predicted temozolomide benefit through interaction testing, supporting the use of adjuvant temozolomide across molecular risk strata within IDH-mutant astrocytoma (search).
Treatment Sequencing Matters
The trial's unique 2×2 factorial design allowed investigators to separately evaluate concurrent and adjuvant temozolomide approaches. The "disentangling" analysis within the IDH (search)-mutant group consistently showed that survival advantage aligned with adjuvant temozolomide. Among patients receiving adjuvant therapy, adding concurrent temozolomide did not improve overall survival (HR 0.92, 0.63-1.36).
This finding has important practical implications, as it suggests that the survival benefit is delivered primarily through the 12-cycle post-radiotherapy temozolomide course rather than concurrent administration during radiation.
Post-Progression Treatment Patterns
The analysis revealed that post-progression treatment was common, with 455 of 573 patients (79%) who experienced progression receiving further therapy. Among patients initially treated with radiotherapy alone who later progressed, 129 of 163 (79%) received chemotherapy at progression, and 119 (73%) received temozolomide.
However, this delayed temozolomide administration did not achieve the same survival benefit as upfront adjuvant treatment in IDH (search)-mutant disease, reinforcing the importance of optimal initial treatment sequencing.
MGMT Status Limitations
Contrary to expectations based on other glioblastoma (search) studies, MGMT (search) promoter methylation status was not prognostic or predictive for temozolomide benefit in IDH-mutant astrocytoma (search). The analysis found poor correlation between different MGMT assessment methods and no clear relationship with treatment response.
Clinical Implications
As corresponding author Martin J. van den Bent from the Brain Tumor Center at Erasmus MC Cancer Institute (search) noted, "Long-term follow-up confirms that radiotherapy followed by 12 cycles of adjuvant temozolomide without concurrent temozolomide during radiotherapy improves survival for individuals with aggressive IDH-mutant astrocytoma (search)."
The results provide a stable foundation for current treatment standards in IDH-mutant anaplastic glioma (search) and establish a benchmark for evaluating emerging therapeutic strategies, particularly IDH (search) inhibitors in higher-grade disease. With median survival extending beyond a decade in some patient subgroups, these findings represent a significant advance in the management of this challenging malignancy.