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Abstract A1-67: Prognostic significance of copy number aberrations in Wilms tumor

Tasnim Chagtai, Christina Zill, Linda Dainese, Jenny Wegert, Mariana Maschietto, Gordan Vujanic, , Ivo Leuschner, Peter Ambros, Maureen O'sullivan,
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Abstract: Background and Purpose: Treatment of Wilms tumor (WT) patients under International Society of Paediatric Oncology (SIOP) protocols is currently stratified by staging and histopathology at nephrectomy after neoadjuvant chemotherapy. However, most relapses occur in cases without specific histopathological risk factors, and there is a clinical need for better prognostic biomarkers. Combined loss of heterozygosity (LOH) of 1p and 16q has recently been introduced in the US as an adverse prognostic indicator, while previous work in our and other laboratories suggests that 1q gain may have a similar association with poor outcome. To examine the clinical significance of 1q gain and assess its potential as a WT biomarker, we developed a simple, effective assay that measures its genomic copy number together with that of several other loci of interest, and applied it to a large tumor series. Methods: 686 frozen tumor samples from the SIOP WT 2001 trial (from a total of 7 countries) were assayed using a rapid multiplex ligation-dependent probe amplification (MLPA) assay that was developed and optimized in association with MRC-Holland b.v. to assess the copy number status of 1p, 1q, 16q, WT1, WTX, TP53, MYCN and FBXW7. Analyses were conducted in 3 laboratories, with exchange of a blinded quality assurance sample set. Results: 1q gain was present in 28% (190/686) of the cases. The 5- year Event Free Survival (EFS) rate was 72.6% (95% Confidence Interval (CI), 66.3%-85%) for those with 1q gain and 86.4% (95% CI, 83.4%-89.6%) for those who lacked 1q gain (p=<0.0001). The Overall Survival (OS) rate for 1q gain cases was 86.9% (95% CI, 82.1%-92.1%) compared to 93.8% (95% CI, 91.7%-92.1%) for cases without the aberration (p=0.01). Both the EFS and OS analysis showed a statistically significant poorer outcome for cases with 1q gain, but there was no association with disease stage. 1q gain was associated with a significantly increased risk of disease recurrence (HR = 2.18, p<0.0001). In this analysis the proportions of samples with 1p and 16q loss were respectively 8% and 16%. Both were marginally significant for EFS but in the OS analysis 1p lost its significance. MYCN gain, 4q (FBXW7) loss and 17p (TP53) loss were also associated with adverse outcome. Conclusion: Gain of 1q is a potential adverse biomarker for WT. Its association with high risk histological features after pre-operative chemotherapy and independent impact on survival require assessment in a larger number of patients before consideration for clinical use. Citation Format: Tasnim Chagtai, Christina Zill, Linda Dainese, Jenny Wegert, Mariana Maschietto, Gordan Vujanic, Neil Sebire, Ivo Leuschner, Peter Ambros, Maureen O'Sullivan, Christophe Bergeron, David Gisselsson, Marcel Kool, Marry van den Heuvel-Eibrink, Norbert Graf, Harm van Tinteren, Aurore Coulomb, Manfred Gessler, Richard Williams, Kathy Pritchard-Jones. Prognostic significance of copy number aberrations in Wilms tumor. [abstract]. In: Proceedings of the AACR Special Conference on Translation of the Cancer Genome; Feb 7-9, 2015; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(22 Suppl 1):Abstract nr A1-67.
Keywords: copy number / TP53 / quality assurance / Fbxw7 / histopathology / Biomarker / chemotherapy / paediatric / Nephrectomy

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