Prediction of metastasis to mesorectal, internal iliac and obturator lymph nodes according to size criteria in patients with locally advanced lower rectal cancer

Abstract

Objective: This study was performed to clarify whether size criteria could be applied to the prediction of metastasis to the mesorectal, internal iliac and obturator lymph nodes in patients with lower rectal cancer. Methods: A total of 915 lymph nodes (416 mesorectal, 199 internal iliac and 300 obturator) from 53 patients with lower rectal cancer who underwent a curative resection were examined; 83 lymph nodes were positive. The sizes of the lymph nodes immediately after removal and those of paraffinembedded sections were compared for 175 lymph nodes. Then, size criteria for discriminating the status of metastasis were evaluated in 915 paraffin-embedded lymph nodes. Results: Regardless of the metastatic status and the site of the lymph nodes, a positive relationship was observed between the sizes of the lymph nodes immediately after removal and those of paraffinembedded sections (P < 0.01). The area under the curve generated by a receiver-operating characteristics curve showed no significant differences between the short-axis diameter and the long-axis diameter, regardless of the lymph node location. Specifically, the optimal cutoff value of the short-axis diameter for discriminating the status of metastasis in mesorectal, internal iliac and obturator lymph nodes extrapolated to the living body was set at 6.2, 5.0 and 4.8 mm, with accuracies of 72.4, 63.8 and 59.3% and with positive predictive values of 29.9, 16.3 and 7.1%, respectively. Conclusions: Size criteria were applicable for discriminating the metastatic status of lymph nodes from three different locations, although the positive predictive values of the size criteria for the internal iliac and obturator lymph nodes were lower than that for the mesorectal lymph nodes.

Pre-operative Evaluation of Lateral Pelvic Lymph Node Metastasis in Lower Rectal Cancer: Comparison of Three Different Imaging Modalities

“…7 mm. We previously reported that the sensitivity of detecting metastatic mesorectum lymph nodes was 90% when the cut-off value of the short axis diameter was set at 6.2 mm [14]. In that study, we confirmed that a short axis size of approximately 5 mm was sufficient to detect LPLN metastasis [14].…”

“…We reported that the optimal short axis cut-off value for determining the metastasis status in LPLN was ! 6 mm in the living body [12,14]. Based on our previous results, in this study, LPLNs larger than 6 mm in their short axis diameter in the MRI and MDCT images were diagnosed as positive of metastasis.…”

“…In this study, we pre-operatively evaluated the regionbased diagnostic values of the three imaging modalities for detecting LPLN metastasis in LRC patients who underwent ME and LPLN dissection without pre-operative chemoradiation, to assess the optimal pre-operative diagnosis strategy, based on criteria established in our previous studies [12,14].…”

Correlations between the sizes of lateral pelvic lymph nodes and metastases in rectal cancer patients treated with preoperative chemoradiotherapy

“…17 However, the PPVs in their study were below 20%, which were even lower than those estimated in our study for LLNs treated with CRT. 17 However, the PPVs in their study were below 20%, which were even lower than those estimated in our study for LLNs treated with CRT.…”

“…Hatano et al reported that the PPVs of the sizes of resected LLNs were low compared to those of the mesorectal lymph nodes of patients treated with surgery alone without CRT. 17 However, the PPVs in their study were below 20%, which were even lower than those estimated in our study for LLNs treated with CRT. Therefore, the sizes of LLNs treated with CRT might be more diagnostically revealing than those of LLNs not treated with CRT.…”