Date Published: March 31, 2017
Publisher: Public Library of Science
Author(s): Jiwon Koh, Hee Eun Lee, Woo Ho Kim, Hye Seung Lee, Ju-Seog Lee.
We aimed to investigate effect of increased number of examined lymph nodes (LNs) to pN category, and compare various N categories in gastric cancer: American Joint Committee on Cancer (AJCC) 7th edition, metastatic LN ratio (MLR), and log odds of positive LNs (LODDS).
Four cohorts with a total of 2,309 gastric cancer patients were enrolled. For cohort 1 and 2, prognostic significance of each method by disease-specific survival was analyzed using Akaike and Bayesian information criterion (AIC and BIC).
The total LNs in four cohorts significantly differed [median (range), 28 (6–97) in cohort 1, 37 (8–120) in cohort 2, 48 (7–122) in cohort 3, and 54 (4–221) in cohort 4; p<0.001]. The numbers of negative LNs increased with increase of total LN (p<0.001), but the numbers of metastatic LNs did not increase from cohort 1 to 4. MLR and LODDS in four cohorts had decreasing tendency with increase of total LNs in each pT3 and pT4 category (p<0.001), while the numbers of metastatic LNs did not differ significantly in any pT category (p>0.05). The AIC and BIC varied according to different cut-off values for MLR; model by cut-offs of 0.2 and 0.5 being better for cohort 1, while cut-offs 0.1 and 0.25 was better for cohort 2.
Our study showed that the number of metastatic LNs did not increase with maximal pathologic examination of regional LNs. AJCC 7th system is suggested as the simplest method with single cut-off value, but prognostic significance of MLR may be influenced by various cut-offs.
Gastric cancer (GC) is one of the most common types of cancer and the leading causes of death, accounting for 10% of total cancer-associated deaths worldwide . In South Korea, about 35,000 people are newly diagnosed with GC annually, and it is the third most common cause of cancer mortality . Lymph node (LN) involvement has long been considered to be the most important prognostic factor in GC . The AJCC 7th edition staging system uses the absolute number of positive LNs to assess the N status, which has long been accepted as the routine way of evaluating regional LN status [4,5].
A total of 2,309 patients who had been diagnosed with GC and consecutively undergone surgical resection at two individual institutions were included in this study. 664 patients were treated at Seoul National University Hospital (Seoul, Republic of Korea) in 2004 (cohort 1). The remaining 1,645 patients were treated at Seoul National University Bundang Hospital (Seongnam, Republic of Korea): 579 patients between January 2003 and December 2005 (cohort 2) and 587 and 479 patients in the years 2011 (cohort 3) and 2013 (cohort 4), respectively. The cases consisted of primary and sporadic GCs; recurred, metastatic, or hereditary cancers were excluded. None had received preoperative chemotherapy or radiotherapy. The patients with stage II to IV disease received adjuvant chemotherapy using fluoropyrimidine (5-fluorouracil, capecitabine, or S-1) alone or fluoropyrimidine plus mitomycin C, cisplatin, or oxaliplatin, if clinically indicated.
In this study, we compared the numbers of total, negative, and metastatic LNs in four independent cohorts to clarify clinical significance of maximal pathologic evaluation of LNs. The numbers of examined LNs of our study far exceeded those of previous studies from various institutions [11,12,19]. Based on the results of previous studies on this topic, we have expected that increased number of examined LNs would probably result in an increased number of positive LNs [12,13]. However, the number of negative LNs increased with the increase of total LN, but the number of metastatic LNs did not.