Published online Apr 15, 2020. doi: 10.4251/wjgo.v12.i4.435
Peer-review started: November 21, 2019
First decision: December 12, 2019
Revised: February 12, 2020
Accepted: February 23, 2020
Article in press: February 23, 2020
Published online: April 15, 2020
Processing time: 146 Days and 1.2 Hours
The reliability of preoperative diagnosis of nodal metastasis of advanced gastric cancer by multi-detector spiral computed tomography (MDCT) is still unclear. A preoperative nodal diagnosis by MDCT is made on the assumption that the size of the metastatic lymph node is large. However, pathological metastatic lymph nodes may not be necessarily large in size.
A one-to-one correspondence between lymph nodes confirmed on preoperative images and those assessed pathologically have not been reported to date. In our hospital, all dissected nodes are usually harvested by experienced surgeons and mapped individually. By measuring the size of the lymph node during harvest, pathological metastasis lymph nodes could be detected precisely by using preoperative MDCT.
The purpose of this study was to examine the preoperative nodal diagnostic ability of MDCT more precisely by using postoperative lymph node mapping and data on pathological metastatic patterns.
A total of 108 patients with advanced gastric cancer who underwent MDCT and curative gastrectomy were enrolled in this study. The nodal sizes measured on computed tomography (CT) images were compared with the pathology results. A receiver-operating characteristic curve was constructed, from which the critical value (CV) was calculated by using the data of the first 69 patients retrospectively. By using the CV, sensitivity and specificity were calculated with prospectively collected data from 39 consecutive patients. This enabled a more precise one-to-one correspondence of lymph nodes between CT and pathological examination by using the size data of lymph node mapping. The intranodal pathological metastatic patterns were classified into the following four types: Small nodular, peripheral, large nodular, and diffuse.
Although all the cases were clinically suspected as having metastasis, 81 had lymph node metastasis and 27 had no metastasis. The number of dissected, detected on CT, and metastatic nodes were, 4241, 897, and 801, respectively. The CV obtained from the receiver-operating characteristic was 7.6 mm for the long axis. The sensitivity and specificity of the diagnostic ability of MDCT for nodal metastasis were respectively 86.8% and 80.1% in the retrospective phase. To verify the accuracy of the CV, diagnostic abilities were calculated using the data from prospective study phase. By referring to the sizes and serial numbers of the lymph nodes measured in the map, a one-to-one correspondence becomes possible between lymph nodes detected by MDCT and the pathological results in the prospective study. The sensitivity was 91.4% and the specificity was 47.3% in the prospective phase. Only 43.8% of the metastatic lymph nodes were larger than the critical values. The larger nodes were only 28.1% of all the peripheral type nodes and 52.7% of the large nodular or diffuse type nodes.
The ability of MDCT to contribute to a nodal diagnosis of advanced gastric cancer was examined prospectively with precise size data from node mapping, using a CV of 7.6 mm for the long axis that was calculated from the retrospectively collected data. The sensitivity was as high as 91%, and would be improved when referring to the enhanced patterns. The nodal diagnosis of cases with the large nodular or diffuse pattern was slightly easier. However, its specificity was as low as 47%, because most of metastatic nodes in gastric cancer being small in size. The small nodular or peripheral type metastatic nodes were often small and considered difficult to diagnose.
Obvious node-positive cases of advanced gastric cancer suitable for neoadjuvant chemotherapy can be identified using MDCT because the sensitivity for the nodal diagnosis was as high as 90% with the critical value of 7.6 mm for the long axis. However, the specificity was as low as 47%, so it seemed difficult to decide the omission of nodal dissection on the basis of the MDCT finding.