Abstract
464^ Background: A new diagnostic semi-automated system, One Step Nucleic Acid Amplification (OSNA), was designed for the detection of cytokeratin 19 (CK 19) mRNA in lymph node (LN) metastases of colon cancer (CC) patients (Güller U et al. CANCER 2012: DOI 10.1002/cncr.27667). Recently it has been shown that occult metastases detected in pN0 patients have an adverse effect on survival based on stage migration. In this study we investigated whether pN0 patients diagnosed by standard histopathology can be upstaged by OSNA analysis to stage III. Methods: In this international, multicenter (4 institutions: CH, G [2], E) study 103 patients-originally diagnosed as pN0 by the standard use of 1 single section haematoxylin & eosin (H&E)-were subjected to OSNA analysis. LN were isolated from fresh tissue, homogenised, and directly subjected to OSNA without prior isolation of mRNA. OSNA results were provided in qualitative categories (- / + / ++), along with the exact CK19 mRNA copy number (+: 250-5000 copies, ++: >5000 copies). Results: In total, 1,594 LN from 103 CC patients (median 14 LN / patient, range 1-46) were analyzed with OSNA. From the 103 histology pN0 patients 26 were positive with OSNA, resulting in an upstaging rate of 25.2%. Sixteen patients had 1 OSNA positive LN, three had 2, three had 3, and one had 4 positive LNs, resulting in a total of 35 positive LN. Patients with pT1, pT2, and pT4 tumors only had 1 positive LN, while all patients with multiple positive LN were from the pT3 group which also contained 9/10 patients with a (++) OSNA result. Concerning stage categories, 6/37 (16.2%) CC patients with stage I were upstaged and 20/66 (30.3%) patients with stage II. Conclusions: OSNA is a novel molecular tool for LN upstaging in CC patients with similar performance as very intensive histological investigation (Güller U et al. CANCER: 2012 DOI 10.1002/cncr.27667). The present study confirms that OSNA improves staging in CC patients and provides a standardized, observer-independent technique for a more accurate staging than the standard histopathology.
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