Integration of next-generation RNA sequencing-based MammaPrint and BluePrint analysis in clinical decision making: Performance evaluation in the first 1095 cases.

Abstract

e12523 Background: Currently, multigene signatures (MGS) such as MammaPrint and BluePrint (MP/BP) have become a cornerstone for selecting breast cancer patients with luminal disease for the use of adjuvant chemotherapy. MP/BP is mainly performed centrally at Agendia in the United States using a cDNA microarray-based technique. We have recently implemented a decentralized Next-Generation RNA Sequencing-Based (RNA-seq) MP/BP test, which can be performed on total RNA extracted from formalin-fixed paraffin-embedded breast cancer tissue. Here we document the technical performance and feasibility of the MP/BP RNA-seq test in a referral University Hospital in Belgium, functioning as national testing facility for MGS. Methods: From December 2019 till August 2022, metrics of the MP/BP RNA-seq tests performed at the University Hospitals Leuven (UHL) were retrieved from the database of the Department of Pathology. Metrics included the number of tests passing the internal quality control, turn-around times, MP and BP indices. Data were collected in a pseudonymized fashion, with no clinical information or follow-up for the purpose of this abstract. Results: A total of 1095 MP/BP RNA-seq tests were performed in UHL representing 42% (n = 1095/2598) of the total national MGS output for the given period. The majority of the tests, 73% (n = 797/1095), were requested by external breast clinics officially recognized by the Belgian Health Care National system while 27% of test requests (n = 298/1095) originated from UHL. The overall failure rate after failed test was 7% (n = 75/1095), being nearly the same for UHL samples (6%) and external samples (7%). As per internal policy the test is repeated after first failure, resulting in substantial reduction of the overall failure rate to ~5%(n = 51/75). The turnaround time measured for 2021 was 13 calendar days (range: 9-27 days), on average. The MP/BP RNA-seq test revealed a Low-risk/Luminal Type A result in 57% (n = 582/1020), High-risk/Luminal Type B in 42% (n = 429/1020), High-risk/ Basal-type and High-risk/HER2-Type in ~1% of the patients (respectively 7 and 2 cases). Further stratification of the MP index showed MP High-risk 2 in 5% (n = 48/1020), MP High-risk 1 in 38% (n = 389/1020), MP Low-risk in 42% (n = 433/1020) and MP Ultra-low risk in 15% of the patients (n = 150/1020). Based on these results, 437/1020 patients (42.8%) would have been recommended adjuvant chemotherapy. Conclusions: Decentralization of the MP/BP RNA-seq test is feasible with low failure rates and acceptable turnaround time. Our results implicate the potential omission of adjuvant chemotherapy in more than half of the patients tested. Further analysis of the MP/BP RNA-seq test in clinical decisions making and clinical follow-up of patients is warranted.