PATH-21. CLINICAL UTILITY OF DNA METHYLATION PROFILING FOR DIAGNOSIS OF CHALLENGING CENTRAL NERVOUS SYSTEM TUMORS: THE TORONTO EXPERIENCE
Bibliographic record
Abstract
Abstract The update on the WHO classification of central nervous system (CNS) tumors incorporated molecular signatures for a more accurate diagnosis. Recently, DKFZ has demonstrated the utility of DNA methylation profiling(MP) for molecular classification of CNS tumors. We performed a prospective clinical study over the last three years to evaluate the clinical utility ofDNA MP on FFPE samples of 66 challenging CNS tumor cases using online DKFZ classifier. Eleven samples were excluded due to low tumor DNA content or low calibration(predictive) scores(CS)< 0.3.DNA MP confirmed the original pathology diagnoses in 15(27%)cases. The integrated molecular diagnoses were changed in 38/55(70%) including establishment of a new diagnostic entity, change in molecular signature and subtyping. TheWHO grades were changed in 16(27%) of the tumors; about two-thirds resulted in upgrading. We detected non-canonical IDH mutations in 9 diffuse gliomas and the CNV plots revealed false positive FISH results for 1p/19q co-deletion in two diffuse gliomas. The CNV plots contributed to the final diagnosis in 40(72%) patients. The molecular subtypes of medulloblastoma, ependymoma and glioblastoma subclasses were determined in 36(65%) cases. Seventy-five percent of cases with confirmation of initial diagnosis or change in molecular diagnosis had CS > 0.5, among which 51% had a CS >0.9. The median and range CS of cases with new diagnostic entity and confirmed cases were 0.86(0.37–0.99) and 0.98(0.42–0.99), respectably. Furthermore, we detected higher CS in IDH-mutant gliomas in comparison to glioblastoma IDH-wild type(P=0.04). We also observed lower CS in mesenchymal glioblastoma in comparison to other subclasses. The MGMT promoter methylation was determined in 17/20(85%) glioblastoma cases. While the DKFZ group established CS of 0.9 as a cut-off for matching to methylation classes, our findings suggest lower threshold values in challenging CNS tumor cases. Our experience indicates clinical utility of MP of challenging CNS tumors as a reliable ancillary diagnostic tool in routine neuropathology practice.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".