Utility of the OSNA assay in sentinel node mapping for early gastric cancer.

Abstract

13 Background: Recent studies on sentinel node (SN) mapping for early gastric cancer have shown acceptable results in terms of detection rate and accuracy to determine lymph node (LN) status. Accurate detection of nodal metastasis including micrometastasis during surgery is indispensable for clinical application of minimized gastrectomy based on SN mapping and biopsy. However, histopathological diagnosis of micrometastasis using frozen sections has to be considered as limitations for intraoperative pathology. We hypothesized that one-step nucleic acid amplification (OSNA) assay may allow the PCR-based intraoperative diagnosis to be applicable to SN mapping for early gastric cancer. Methods: A prospective study of SN mapping using the OSNA (One-step nucleic acid amplification) assay has been conducted for patients with cT1N0M0 gastric cancer at our institution. All SNs and randomly selected non-SNs were examined by routine histopathological diagnosis and the OSNA assay. Results: Histological examination was performed in in 1,732 LNs (286 SNs and 1,446 non-SNs) from 43 patients with cT1N0M0 gastric cancer. We also evaluated 439 LNs (286 SNs and 153 non-SNs) with histological examination and the OSNA assay from the 43 patients. Histological LN metastasis was revealed in 6 (14.0%) of 43 patients. All (100%) of the 6 patients with LN metastasis showed positive SNs by histological examination. The diagnostic accuracy to predict the LN status based on SN concept by histological examination was 100%. The concordance rate between the OSNA assay and the histological examination of paraffin specimens was 0.970 (95 % CI, 0.950–0.984). Discordant results were observed in 13 LNs (3.0 %). Sensitivity and specificity of the OSNA assay compared to the histological examination were 0.636 (95 % CI, 0.407–0.828) and 0.988 (95 % CI, 0.972–0.996), respectively. The OSNA assay to evaluate the SNs status was comparable with intraoperative pathological diagnosis of frozen sections of SNs in terms of concordance rate (0.981), sensitivity (0.800) and specificity (0.995). Conclusions: Our results suggest that the OSNA assay may be a useful tool for the intraoperative detection of metastasis in SNs for patients with early gastric cancer.