Limited lymph node dissection and metastatic lymph node ratio: a wave of trust.

To the Editor Metastatic lymph node ratio has been closely investigated in recent years because of its simplicity, reproducibility, and potential advantage of reducing the ‘‘stage migration’’ phenomenon in gastric cancer staging. Several authors, along with our experience, identified the lymph node ratio classification as an independent prognostic factor stronger than AJCC/UICC and JGCA classifications [1]. Moreover, this classification might be usefully implemented in any clinical practice, not being influenced by differences in the routine extension of lymph node dissection [2]. Pedrazzani et al. [3] report a retrospective series of a 526 patients with gastric cancer who underwent limited lymph node dissection and had a small (\15) number of analyzed nodes. In this series, they investigated the prognostic significance of lymph node ratio with cutoff values as follows: N ratio 0 (pNR0), 0%; N ratio 1 (pNR1), 1–25%; and N ratio 2 (pNR2), 25%. In their analysis no significant differences in survival were observed between pN1 and pN2 subsets. When the N ratio (1–25% vs. 25%) was taken into account, a significant difference was demonstrated between pNR1 and pNR2 with respect to survival (p = 0.017) and risk of death (p = 0.012). These results notwithstanding, the authors claimed a poor clinical utility of metastatic lymph node ratio because of poor allocation of patients in pNR1 category. Some features of data interpretation of this study warrant further assessment. First, the allocation of patients in pNR1 was poor as well as the allocation in pN2. At the same time, pNR classification significantly stratified patient outcome, whereas pN did not. I wonder why these results could not be considered of clinical utility. Should we need another more powerful prognostic factor? Second, the authors stated that the in pN1 category and in patients with one to three metastatic nodes, metastatic lymph node ratio can discriminate a subset of patients with better prognosis. In our opinion these results are in agreement with the changes proposed by the new seventh edition of AJCC/UICC [4] staging rules, whereas the old pN1 category will be subdivided in pN1 (1–2 metastatic lymph nodes) and pN2 (3–6 metastatic lymph nodes). By other means, in this study, the metastatic lymph node ratio was able to discriminate these patients. Third, the goal of cancer staging is to aid the clinician in planning treatment, to give some indication of prognosis, and to assist in evaluating the results of treatment. UICC/AJCC staging rules certainly represent the best system to estimate cancer prognosis but unfortunately are still affected by both surgical treatment and pathologic assessment; these ‘‘human’’ variables will always have strong impact on staging until they are universally standardized. In gastric cancer the appropriate extent of lymph node dissection continues to be debated and pathologic evaluation of gastric specimens constitutes a source of significant bias [5]. Considering these unsolved issues, in our opinion, metastatic lymph node ratio provides a meaningful prognostic factor when an official staging system cannot be applied and minimum data are lacking. A. Biondi (&) R. Persiani F. Cananzi M. Zoccali A. Tufo D. D’Ugo 1st General Surgery Unit, Department of Surgery, Catholic University, Largo A. Gemelli 8, 00168 Rome, Italy e-mail: biondi.alberto@tiscali.it