Elsevier

European Journal of Cancer

Volume 41, Issue 14, September 2005, Pages 2071-2078
European Journal of Cancer

Cancer staging and survival in colon cancer is dependent on the quality of the pathologists’ specimen examination

https://doi.org/10.1016/j.ejca.2005.06.012Get rights and content

Abstract

Correct staging of colon cancer is decisive regarding further oncological treatment, surveillance and prediction of long-term survival. This study investigated the variability in accuracy of pathology reports with focus on differences between pathology departments and their compliance to regional guidelines. Data from the colon cancer register (1997–2002) of the Uppsala/Örebro, Sweden, health care region were analysed and the seven pathology departments in this region were compared. Included were 3735 patients who had undergone resection of a colon cancer. Cumulative 5-year survival was the main end-point.

For 64% (n = 2390) of the cases, the number of lymph nodes examined was given (median 8). Survival in stage II was lower when fewer than 12 nodes were examined or when the number of nodes sampled was not given (P = 0.001, log-rank test). In stage III, those with at the most 3 nodes positive (N1) had a better survival than those with 4 or more nodes positive (N2) (P < 0.001, log-rank test). An index of metastases (IM), derived from the number of nodes with metastases divided by the number of nodes examined, was calculated for stage III tumours. Examination of 12 nodes is necessary to assure stage III cases with the median IM (0.32), whereas 20 nodes are necessary to assure 90% of cases with the lower quartile of IM (0.16). Irrespective of the number of nodes investigated, overall survival was better among patients with IM < 0.33 vs. IM  0.33 (P < 0.001, log-rank test). The prognostic information of the IM was higher than that of the N-stage. Quality of a pathology department, measured by the median number of lymph nodes investigated and by the proportion of reports where the number is given, was determined to indicate correct staging and management of the patient. An index of metastases (IM) is a possible basis for guidance in the choice of adjuvant treatments that appears superior to that of N-stage.

Introduction

The staging of patients operated for colon cancer is a determining factor for further oncological treatment and for prediction of long-term survival. Different staging systems for classification have been used since Dukes introduced his classification system for rectal cancer in 1932 [1], and most commonly used today is the TNM classification [2]. As several studies have shown that postoperative chemotherapy in patients with a stage III colon cancer has a beneficial effect on survival 3, 4, 5, it is even more important to improve not only the surgical technique, but also sampling of nodes and staging. There appears to be a breakpoint in the number of lymph nodes examined that will properly determine the proportions of tumour stages II and III [6].

During the past decade, the surgeon and the surgical technique have been in focus in research concerning quality and survival in colorectal cancer 7, 8, 9, 10, 11. An important recent step in attempts to further improve the surgical quality in rectal cancer has been the provision for immediate feedback from the pathologist to the surgeon [12]. Important advances have also been made in pre- and post-operative oncological treatment 3, 13. However, a prerequisite for a proper decision by the oncologists about postoperative treatment is a valid report from the pathologist after examination of the resected specimen. Several attempts have been made to estimate the number of nodes necessary to examine for correct staging. Between 6 and 18 nodes have been recommended 14, 15, 16. According to the World Congress of Gastroenterology (Sydney, Australia, 1990) [6], a minimum of 12 lymph nodes should be examined for correct classification of tumours as stage II.

In population-based studies, the proportions of colon cancer in stages II and III are approximately 40% and 30% 17, 18, 19, with survival rates varying between 50–80% and 30–60%, respectively. However, there are reasons to believe that the proportion of stage III tumours is in fact higher than has been reported, on account of inadequate examination of lymph node metastases. During the past decade it has been considered a gold standard to offer adjuvant chemotherapy to patients operated on for a colon cancer stage III, as several studies have shown that this increases survival by approximately 10%, whereas this is not yet the case in stage II where uncertainties about the value of adjuvant chemotherapy still exist 3, 5, 20, 21. It is therefore of immediate importance to identify all patients with lymph node metastasis.

The aim of this study was to investigate the variability in the accuracy of pathology reports, with special attention to differences between pathology departments and to their compliance to regional guidelines. Since the number of nodes is influenced by preoperative radiotherapy, frequently used for rectal cancer [13], and a clear survival benefit of postoperative chemotherapy has been found for colon, but not for rectal cancer, our investigation was focused solely on colon cancer. Our primary hypothesis was that the differences in quality between pathology departments influence the classification of tumours into stages and that stage dependent outcome was influenced by the quality.

Section snippets

Materials and methods

Since 1997 all colon cancers (adenocarcinoma) in the Swedish health care region of Uppsala/Örebro (population 1.9 million in 2001) have been reported to a population-based register run by the Regional Oncologic Centre (ROC). During this period, common regional guidelines for diagnosis, staging and treatment of colorectal cancer have been settled and agreed upon in consensus, by surgeons, oncologists and pathologists. The guidelines include, among others, recommendations concerning the

Results

Characteristics of the included patients are listed in Table 1. In 64% (n = 2390) of the cases, the number of lymph nodes examined was given in the pathology report. In these, the median overall number of lymph nodes examined was 8 (mean 9.4), with a variation in medians between pathology departments from 6 to 12 lymph nodes (Table 2). During the study period, an improvement was seen regarding the proportion of reports where the number of nodes examined was given (20% in 1997 and 90% in 2002) as

Discussion

In the present population-based study, the number of nodes examined was recorded in 64% of the cases and only 19% of the examinations fulfilled the recommendations regarding a minimum of 12 examined nodes and that the number examined should be stated.

Our data were taken from the colon cancer registry, and not directly from the pathology report. However, a previous validation of the registry [23] showed that missing data (regarding number of lymph nodes examined) is not due to improper reports

Conflict of interest statement

None declared.

Acknowledgements

This study was approved by the Regional Oncological Centre, University Hospital, Uppsala, with special help from Hans Garmo, statistician. Financial support was obtained from the Swedish Cancer Society (Grant No. 1921-B04-22xAC).

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