Number of lymph nodes examined and prognosis of TNM stage II colorectal cancer
Introduction
For patients undergoing curative surgery for colorectal cancer (CRC), it is critically important to accurately differentiate between the group with localised or node-negative disease (TNM stage II) and the group with regional or node-positive disease (TNM stage III), since this has a significant effect on prognosis and treatment. Five-year survival for stage II CRC is 70–75% [1]; survival for stage III CRC is 45% [1], [2]. Patients with stage III CRC are routinely offered postoperative adjuvant chemotherapy, whereas those with stage II CRC are not [2], [3], [4].
Nevertheless, the outcome for TNM stage II patients remains highly variable, with a number of patients faring worse than those with apparently more advanced tumours. A proportion of these disappointing outcomes may be explained by understaging [5]. Adequate retrieval and assessment of colorectal mesenteric lymph nodes is critical to ensure that the lymph nodes do not contain metastatic disease. Failure to examine enough lymph nodes may result in a failure to identify patients in whom lymph nodes are affected by cancer and thus may result in understaging [6]. Several studies have examined the relationship of the number of lymph nodes examined to the prognosis of stage II CRC, [6], [7], [8], [9], [10], [11], [12] and some of these have attributed understaging to the worse prognosis of those cases in which few lymph nodes had been examined [5], [6], [7]. However, other authors have hypothesised that a smaller number of lymph nodes examined reflects differences in the biologic behaviour of the tumour and/or host, such as a diminished immune response [5]. The differing results of the studies carried out on this subject could be attributed to differences in the methods used. Studies based on large numbers of cases [6] yield results that are statistically reliable, but are multicentric; it would be reasonable to assume that different pathologists use different techniques and degrees of diligence in examining specimens for lymph nodes, and that there may be some variability in the extent of dissection by different surgeons. Monocentric studies reduce the variation in the pathologist’s examination and in the surgical techniques, although those available in the literature refer to limited sample sizes [5], [9], [10], [11], [12]. Tepper and colleagues [8] reviewed data from a relatively large prospective rectal cancer trial (1664 patients), but the report did not address patients with colon cancer.
The aim of this study was to determine whether the number of lymph nodes examined has an effect on prognosis of a relatively large sample of patients who underwent curative surgery for stage II CRC at a single institution.
Section snippets
Patients and methods
The notes on all patients undergoing surgery for CRC in the General Surgical Clinics and Surgical Therapy Section of the Surgical Sciences Department at the University of Parma, Italy, between January 1980 and April 2000, were prospectively collected in a database. Patients with a known history of familial adenomatous polyposis or cancer, those with Crohn’s disease or ulcerative colitis, and those with synchronous or recurrent tumours were excluded. All tumours were staged according to the TNM
Results
During the study period, 745 cases of T3-4N0 (stage II) and, for comparison purposes, 493 cases of T3-4N1-2 (stage III) colon cancer were reported. The exact number of lymph nodes examined was not clear for 65 stage II and 43 stage III patients, and 11% of all cases were reported as lost to follow-up; these cases were considered as being unsuitable for the study, leaving 625 stage II and 415 stage III patients for further statistical analysis. Clinical and pathological data, and details
Discussion
In our patient group, the age and gender distribution were comparable to other published studies, as were the survival figures.
The results of this study confirm the opinion that the number of lymph nodes examined is a prognostic variable for patients with TNM stage II CRC. Besides the number of lymph nodes, the depth of tumour invasion, age and gender were also prognostic variables for this group. The significance of age is not clear from this analysis, although it may be related to comorbid
Conflict of interest statement
None declared.
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