Abstract CT278: <i>ERBB2</i> amplification detected in ctDNA as a surrogate for tumor tissue FISH analysis of HER2 status in a phase 1 study with zanidatamab for the treatment of locally advanced or metastatic HER2 expressing cancers
Bibliographic record
Abstract
Abstract Background: HER2-targeted therapies have substantially improved outcomes for patients with HER2-positive breast and gastric cancers. Several other cancers exhibit HER2 expression and/or amplification of its gene (ERBB2), suggesting that HER2-targeted agents may have broader therapeutic utility. Zanidatamab is a humanized, novel bispecific antibody directed against two non-overlapping domains of HER2. The aim of this Phase 1 dose-escalation and expansion study (NCT02892123) was to evaluate the safety and efficacy of zanidatamab across a range of solid tumors. Parallel to drug development, there has been rapid advancements in NGS technologies including the Guardant360 assay that can specifically sequence ctDNA and detect amplifications of the ERBB2 gene, which can lead to overexpression of HER2. FISH, the current gold standard for HER2 amplification detection, is a tissue-based assay that assesses the raw ERBB2 copy number as well as ratio of ERBB2 to a centromeric protein of chromosome 17 where the ERBB2 gene resides. We evaluated concordance of the FISH and Guardant360 assays to detect ERBB2 amplification in plasma samples. Unlike gene copy number in tissue analysis, the observed plasma copy number (pCN) is also a function of the tumor burden and rate of tumor shedding of ctDNA into the bloodstream. Methods: HER2 status was determined from a fresh tumor biopsy or in archival FFPE tissue samples by IHC and FISH according to ASCO-CAP guidelines from the Phase 1 study with zanidatamab in multiple cancer types (cholangiocarcinoma [21], colorectal carcinoma [27], all other [87]). Plasma samples were collected prior to the first cycle of zanidatamab and on-treatment for testing with Guardant360, 74 gene ctDNA NGS-based assays. Results: A concordance of 82% was observed in ERBB2/HER2 amplifications between the Guardant360 and FISH assays. An exploratory adjustment method based on tumor DNA shedding was developed by Guardant using the maximum mutant allele fraction (maxVAF) as a surrogate for tumor content. Majority of patients experienced a decrease in HER2 pCN post treatment, with 9 PD patients having the least and 21 PR patients the largest changes in ctDNA fraction (maxVAF). Conclusion: These results indicate that ERBB2 amplification detected by the Guardant360 assay could be used as a surrogate for FISH analysis in lieu of invasive surgical procedures. Citation Format: Diana Shpektor, Daryanaz Dargahi, Antonios Samiotakis, Sara Wienke, Ali Livernois, Arielle Yablonovitch, Geethika Yalamanchili, Elaina Gartner, Funda Meric-Bernstam. ERBB2 amplification detected in ctDNA as a surrogate for tumor tissue FISH analysis of HER2 status in a phase 1 study with zanidatamab for the treatment of locally advanced or metastatic HER2 expressing cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT278.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.005 | 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".