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In Reply

Brigham and Women's Hospital and Dana-Farber Cancer Institute, Boston, MA

In Reply:

The letter authored by Drs Pocard et al reiterates many of the issues we considered during the design and analysis of our study.¹ The concerns expressed involve the following three areas: (1) the effect of surgeon experience on success of sentinel lymph node sampling (SLNS) technique; (2) the adequacy of multilevel sectioning and immunohistochemical (IHC) staining for detecting micrometastatic disease (MMD); and (3) the overall purpose of the study (ie, to determine whether SLNS is an acceptable method of simplifying analysis of MMD in large clinical trials).

We examined the effect of surgeon experience on our results. From the 12 clinical centers involved in the study, 25 qualified surgeons participated. We determined the relationship between number of SLNSs performed and likelihood of finding either no sentinel lymph node (SNs) or an SN that did not predict the status of the nodal basin. Failure to detect a predictive SN occurred in 33% of attempts for the two surgeons who performed 10 or more SLNSs, in 16% of attempts for surgeons who performed five to nine SLNSs, and in 40% of attempts for surgeons who performed less than five SLNSs. Therefore, we conclude that on-study experience did not affect ability to detect SNs for this group of 25 surgeons who were already familiar with SN procedures for breast cancer and melanoma.

With regard to techniques for detecting MMD, Pocard et al state that "...the main interest of SNS likely relies on upgrading a subset of colon cancer patients staged as N0 (stage II) after conventional regional node histologic examination to node-positive (stage III) patients." They quote selected studies using multilevel sectioning and IHC for upstaging lymph nodes that are negative by conventional histology and indicate that the results of these studies are at odds with our data. We maintain that is it just this level of contradiction in the existing literature that leads us to consider standardization of technique for characterizing MMD to be the essential first step in improving colon cancer staging.

Finally, as stated in the Introduction of our article,¹ the primary purpose of our study was not to determine the effect of SLNS on upstaging colon cancer patients or on surgical procedure for colon cancer by detecting SN outside the conventional regional nodal basin. However, despite the conflicting studies cited by Pocard et al, our results are in agreement with the results of others indicating that SLNS is not useful for these purposes.^2-7 Our primary goal was to determine whether SLNS will facilitate large-scale clinical trials that are necessary to determine whether characterization of MMD will improve conventional regional lymph node staging. Because we found that SNs that are node negative by conventional staging are no more likely than non-SNs to harbor MMD detectable by IHC, we concluded that this technique should not be used to limit the number of nodes examined in trials to determine the clinical significance of MMD.

Authors' Disclosures of Potential Conflicts of Interest

The authors indicated no potential conflicts of interest.

REFERENCES

1. Redston M, Compton CC, Miedema BW, et al: Analysis of micrometastatic disease in sentinel lymph nodes from resectable colon cancer: Results of Cancer and Leukemia Group B Trial 80001. J Clin Oncol 24:878-883, 2006[Abstract/Free Full Text]

2. Bertagnolli MM, Miedema B, Redston M, et al: Sentinel node staging of resectable colon cancer: Results of CALGB 80001 a multicenter study. Ann Surg 240:624-628, 2004[Medline]

3. Bertoglio S, Sandrucci S, Percivale P, et al: Prognostic value of sentinel lymph node biopsy in the pathologic staging of colorectal cancer patients. J Surg Oncol 85:166-170, 2004[CrossRef][Medline]

4. Joosten JJA, Strobbe LJA, Wauters CAP, et al: Intraoperative lymphatic mapping and the sentinel node concept in colorectal carcinoma. Br J Surg 86:482-486, 1999[CrossRef][Medline]

5. Merrie AEH, van Rij AM, Phillips LV, et al: Diagnostic use of the sentinel node in colon cancer. Dis Colon Rectum 44:410-417, 2001[CrossRef][Medline]

6. Patten LC, Berger DH, Rodriguez-Bigas M, et al: A prospective evaluation of radiocolloid and immunohistochemical staining in colon carcinoma lymphatic mapping. Cancer 100:2104-2109, 2004[CrossRef][Medline]

7. Read TE, Fleshman JW, Caushaj PF: Sentinel lymph node mapping for adenocarcinoma of the colon does not improve staging accuracy. Dis Colon Rectum 48:80-85, 2005[CrossRef][Medline]

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Related Correspondence

• Sentinel Lymph Node Sampling and Analysis in Colon Cancer: What Is the Question?
  Marc Pocard, Marc Van den Eynde, Diane Goere, Valérie Boige, and David Malka
  JCO 2006 24: 3712-3713 [Full Text]

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