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Prostate Cancer: Markers (MP60): Moderated Poster 60: Monday, September 13, 2021

MP60-20 DETECTION OF LYMPH NODE METASTASES USING POOLING METHOD BY ONE-STEP NUCLEIC ACID AMPLIFICATION (OSNA) ASSAY IN PROSTATE CANCER PATIENTS: PRELIMINARY RESULTS FROM A PROSPECTIVE-MULTICENTRE STUDY

Cuadras, Mercè; Regis, Lucas; Planas, Jacques; Celma, Ana; Semidey, Ma Eugenia; de Torres, Ines; Ramon y Cajal, Santiago; Congregado, Belén; Baena, Cristina; Japón, Miguel Ángel; de Álava, Enrique; Marcilla, David; Martínez-Piñeiro, Luis; Hardisson, David; González-Peramato, Pilar; García, Eugenia; Buisán, Oscar; Areal, Joan; Fernández, Pedro L.; Fernández, Pedro L.; Carrato, Cristina; Gómez, M. Carmen; Morote, Juan; Trilla, Enrique

doi: 10.1097/JU.0000000000002095.20
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INTRODUCTION AND OBJECTIVE:

Lymph node (LN) status is a key prognostic factor in the decision-making process for prostate cancer (PC) management. Sectioning and haematoxylin-eosin (HE) staining technique remains the gold standard for LN metastases evaluation despite its low sensitivity in detecting an accurate tumor burden. OSNA is a molecular technique able to quantify mRNA copies of cytokeratin19 (CK19) as a surrogate of cancer burden and to analyse the entire LN in a fast, objective, automatable and reproducible way, raising general interest to explore its utility in improving LN staging. The aim of this study is to assess the value of OSNA for the detection of LN metastases in PC compared to standard examination by HE and CK19 immunohistochemistry (IHC).

METHODS:

This is an observational, prospective and multicentric study running out in Spain since September 2019. 37 patients with confirmed intermediate-high risk PC, fit for extended lymphadenectomy, were included. A minimum of 12 LN were removed from each patient, with a total of 729 LN analysed. Positive CK19 IHC was confirmed in every case by pre-surgery biopsy. Written consent was obtained. Patients with neoadjuvant therapies, metastatic PC or those diagnosed of another CK19 expressing tumors were excluded. Removed LN were sectioned in two or more slices depending on its size. One half or the central slice of each LN was submitted to HE and the remaining material to OSNA. Based on breast cancer application, a cut-off value of 250copies of CK19mRNA/µl allows to identify LN as “positive” or “negative”. We assumed a range of 250-˂5000 copies/µl as micrometastases and ≥5000 copies/µl as macrometastases, but specific PC cut-off points should be defined for a more accurate results. Pooling method was performed, so, after LN sectioning, slices designated to OSNA assay were pooled in groups of 6 LN or <650 mg of lymphatic tissue.

RESULTS:

Pathologists detected tumor cells in a total of 13 LN by standard HE technique. Analysis was performed by per patient. Using the mentioned OSNA cut-off value of 250copies/µl, concordance rate between both methods was 86.5%, with a sensitivity of 62.5% and a specificity of 93.2%. Positive predictive value (PPV) was 71.4% and negative predictive value (NPV)90%. Discordant results were reported in 5 patients. 2 cases were H&E and CK19 IHC negative - OSNA positive. The remaining were H&E positive – OSNA negative. 2 of these cases were analysed the day after surgery, assuming that a long time until OSNA analysis could lead to an mRNA disintegration. The third negative OSNA case presented a minimum metastatic volume detected by H&E, what could suggest tumor allocation bias.

CONCLUSIONS:

Preliminary results show that OSNA assay may be a specific technique in detecting CK19 PC lymphatic metastases. There are also promising results regarding PPV and NPV. Higher sensitivity is expected as the number of included cases increase.

Source of Funding:

Non Source of Funding

© 2021 by American Urological Association Education and Research, Inc.