Assessment of structural chromosomal instability phenotypes as biomarkers of carboplatin response in triple negative breast cancer: the TNT trial.
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<h4>Background</h4>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.<h4>Patients and methods</h4>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).<h4>Results</h4>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<sub>HLAMP,quiet</sub> = 0.085; PFS 6.1 months (C) versus 4.1 months (D), P<sub>interaction/HLAMP</sub> = 0.047]. In the carboplatin arm, patients with tumours showing intermediate telomeric NtAI and AiCNA had higher ORR [54% (C) versus 20% (D), P<sub>NtAI,intermediate</sub> = 0.03; 62% (C) versus 33% (D), P<sub>AiCNA,intermediate</sub> = 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<sub>interaction/AiCNA</sub> = 0.027, P<sub>adj.interaction/AiCNA</sub> = 0.125 and P<sub>interaction/PGA</sub> = 0.053, P<sub>adj.interaction/PGA</sub> = 0.176], whilst no difference was observed in the docetaxel arm.<h4>Conclusions</h4>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.
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Antineoplastic Combined Chemotherapy Protocols
Triple Negative Breast Neoplasms
Clinical Trials & Statistics Unit
Genomic Analysis – Clinical Trials
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Annals of oncology : official journal of the European Society for Medical Oncology, 2021, 32 (1), pp. 58 - 65