Assessment of structural chromosomal instability phenotypes as biomarkers of carboplatin response in triple negative breast cancer: the TNT trial

Orsolya Sipos, Holly Tovey, Jelmar Quist, Syed Hyder, Salpie Nowinski, Patricja Gazinska, Sarah Kernaghan, C Toms, Sarah Maguire, Nick Orr, Sabine Linn, Julie Owen, Cheryl Gillett, Sarah Pinder, Judith Bliss, Andrew Tutt, Maggie C.U. Cheang, Anita Grigoriadis

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Abstract

Background: In the TNT trial of triple negative breast cancer (NCT00532727), germline BRCA1/2 mutations were present in 28% of carboplatin responders. We assessed quantitative measures of structural chromosomal instability (CIN) to identify a wider patient subgroup within TNT with preferential benefit from carboplatin over docetaxel. Patients and methods: Copy number aberrations (CNAs) were established from 135 formalin-fixed paraffin-embedded primary carcinomas using Illumina OmniExpress SNP-arrays. Seven published [allelic imbalanced CNA (AiCNA); allelic balanced CNA (AbCNA); copy number neutral loss of heterozygosity (CnLOH); number of telomeric allelic imbalances (NtAI); BRCA1-like status; percentage of genome altered (PGA); homologous recombination deficiency (HRD) scores] and two novel [Shannon diversity index (SI); high-level amplifications (HLAMP)] CIN-measurements were derived. HLAMP was defined based on the presence of at least one of the top 5% amplified cytobands located on 1q, 8q and 10p. Continuous CIN-measurements were divided into tertiles. All nine CIN-measurements were used to analyse objective response rate (ORR) and progression-free survival (PFS). Results: Patients with tumours without HLAMP had a numerically higher ORR and significantly longer PFS in the carboplatin (C) than in the docetaxel (D) arm [56% (C) versus 29% (D), P HLAMP,quiet = 0.085; PFS 6.1 months (C) versus 4.1 months (D), P interaction/HLAMP = 0.047]. In the carboplatin arm, patients with tumours showing intermediate telomeric NtAI and AiCNA had higher ORR [54% (C) versus 20% (D), P NtAI,intermediate = 0.03; 62% (C) versus 33% (D), P AiCNA,intermediate = 0.076]. Patients with high AiCNA and PGA had shorter PFS in the carboplatin arm [3.4 months (high) versus 5.7 months (low/intermediate); and 3.8 months (high) versus 5.6 months (low/intermediate), respectively; P interaction/AiCNA = 0.027, P adj.interaction/AiCNA = 0.125 and P interaction/PGA = 0.053, P adj.interaction/PGA = 0.176], whilst no difference was observed in the docetaxel arm. Conclusions: Patients with tumours lacking HLAMP and demonstrating intermediate CIN-measurements formed a subgroup benefitting from carboplatin relative to docetaxel treatment within the TNT trial. This suggests a complex and paradoxical relationship between the extent of genomic instability in primary tumours and treatment response in the metastatic setting.

Original languageEnglish
Pages (from-to)58-65
Number of pages8
JournalAnnals of Oncology
Volume32
Issue number1
Early online date20 Oct 2020
DOIs
Publication statusPublished - 1 Jan 2021

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