Clinical investigations
Rectum
Impact of preoperative radiation for rectal cancer on subsequent lymph node evaluation: A population-based analysis

Presented at the 2004 Gastrointestinal Cancer Symposium.
https://doi.org/10.1016/j.ijrobp.2004.06.259Get rights and content

Purpose

To determine the impact of preoperative radiotherapy (RT) on the accuracy of lymph node staging (LNS). Preoperative RT is a well-established component of rectal cancer treatment but its impact on LNS is unknown.

Methods and materials

The Surveillance, Epidemiology and End Results (SEER) registry, representing 14% of the U.S. population, was used to assess the impact of preoperative RT on LNS. Our study population consisted of adults with rectal cancer between 1998 and 2000 who underwent radical resection.

Results

In our 3-year study period, 5647 patients met the selection criteria and 1034 (19.5%) underwent preoperative RT. The preoperative RT group was younger (average age, 61 years) than those who did not undergo preoperative RT (average age, 69 years) and more likely to be male (22% of men vs. 16% of women). On average, fewer nodes were examined in patients who underwent preoperative RT (7 nodes) vs. those who did not (10 nodes); this difference was statistically significant, controlling for potential confounders (p ≤ 0.0001). In 16% of the preoperative RT patients (vs. 7.5% without), no nodes were identified (p ≤ 0.0001). If one used a minimum of 12 nodes as the standard, only 20% of patients who underwent preoperative RT underwent adequate LNS.

Conclusion

Lymph node staging in patients who undergo preoperative RT must be interpreted with caution. Studies are needed to evaluate the clinical relevance of node number and pathologic staging after preoperative RT for rectal cancer.

Introduction

Rectal cancer is common and is associated with statistically significant morbidity and mortality (1). The traditional treatment has relied on radical resection. Dissection of lymph node-bearing tissue along with the rectum enables the surgeon to remove any occult direct extension and metastasis to the mesorectum and also ensures adequate staging. Recent studies have identified the prognostic significance of the number of nodes excised by the surgeon and then examined by the pathologist (2, 3, 4, 5, 6, 7, 8, 9, 10). In fact, the International Union Against Cancer requires the presence of at least 12 negative nodes in the surgical specimen to confirm adequate staging in node-negative patients (11). This requirement for 12 nodes has been accepted as the standard in the treatment of rectal cancer (by a panel of experts sponsored by the National Cancer Institute) (12).

In 1990, the National Institutes of Health Consensus Conference established adjuvant radiotherapy (RT) with chemotherapy as the standard of care to achieve regional control of Stage II and III rectal cancer (13). Preoperative RT may well confer real benefits. Its use is significant and may be increasing. In fact, an increasing body of data suggests the superiority of preoperative RT combined with chemotherapy in terms of local control, disease-free survival, and the ability to perform sphincter-sparing resection (14, 15, 16). However, the impact of preoperative RT on pathologic lymph node evaluation has not yet been quantified. Evidence indicates that preoperative RT may decrease the number of analyzable nodes that the surgeon and pathologist are able to retrieve (17, 18, 19). Given the increasing importance of preoperative RT, we designed our study to examine its effect, in a population-based fashion, on pathologic nodal evaluation after radical resection for rectal cancer.

Section snippets

Data

We used the data from the Surveillance, Epidemiology and End Results (SEER) cancer registry, a population-based registry sponsored by the National Cancer Institute. SEER collects information on cancer incidence and survival from 11 population-based cancer registries and three supplemental registries; these registries include about 14% of the U.S. population (20). The information collected by SEER includes patient characteristics, county of residence, primary tumor site, morphologic features,

Results

In our 3-year study period, 5647 patients (58% male) with rectal cancer met our selection criteria. In 5317 patients (94%), the radiation sequence with respect to surgery could be determined. Of these 5317 patients, 1034 (19.5%) had undergone preoperative RT (Table 1). Patients who underwent preoperative RT tended to be younger (average age, 61 years) than those who did not undergo preoperative RT (average age, 67 years). In addition, the men were more likely to undergo preoperative RT (22% of

Discussion

For patients with rectal cancer who undergo primary surgical resection, the number of lymph nodes found and analyzed by the pathologist can have a major impact on outcome (2, 3, 4, 5, 6, 7, 8, 9, 10). For patients with T1 or T2 rectal cancer, who have no lymph node involvement, no additional therapy is usually administered. However, if lymph nodes are involved, adjuvant RT and chemotherapy are generally recommended. In addition, positive lymph nodes have a substantial effect on the patient's

Conclusion

Overall, our study demonstrated that few rectal cancer patients underwent adequate LNS. In light of the impact of nodal retrieval on postoperative care and prognosis, many patients in the United States would benefit from improvements in prevailing surgical and pathologic practices. Various professional organizations must help ensure that patients receive proper surgical care and pathologic assessment. For rectal cancer patients who undergo preoperative RT, additional research is crucial to

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