Originally published as JCO Early Release 10.1200/JCO.2009.21.9600 on April 20 2009

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Reply to C.D. Atkins

Thomas Jefferson University, Philadelphia, PA
Fox Chase Cancer Center, Philadelphia, PA
Radiation Therapy Oncology Group, Philadelphia, PA
University of Maryland, Baltimore, MD
Brown University, Providence, RI
Rush University, Chicago, IL
Duke University, Durham, NC

We would like to thank Dr Atkins¹ for his insightful response to our recent article on the prognostic importance of postoperative CA 19-9 levels in resected pancreatic cancer patients undergoing adjuvant chemoradiotherapy.² In this study, he notes that patients who were Lewis antigen nonexpressors were assigned values of 0 for their CA 19-9 level. This is a legitimate point. In 1987, Tempero et al³ examined the relationship of CA 19-9 and Lewis antigen in pancreatic cancer. In this seminal work, they tested 20 patients for Lewis A and B antigen expression and correlated this with serum CA 19-9 levels. In fact, three (15%) of 20 were negative for both A and B antigen expression. The CA 19-9 levels of these patients were 4, 14, and 10, respectively, which was significantly lower than the other patients in the study.

In Radiation Therapy Oncology Group (RTOG) 9704, red cell phenotyping for Lewis A and B was performed at each enrolling institutions laboratory/blood bank. If the patient was positive for either antigen, serum was forwarded to the RTOG central pathology repository for CA 19-9 testing by enzyme-linked immunosorbent assay. If the enrolling institution found the patient to be Lewis A and B antigen negative, then the patient was assigned to the Lewis antigen–negative (or CA 19-9 nonsecretor) group. We agree that it is not completely accurate to state that they have a 0 value for CA 19-9 since the study by Tempero et al³ shows that these levels are not actually zero. However, we do not believe this detracts from the fundamental significance of our study, which shows that patients with levels 180 have significantly poorer survival. If one examines Figure 2 from the current study,² one notes that the survival curves of patients with CA 19-9 levels less than 180 and those that are Lewis antigen negative are similar and therefore these patients experienced a similar survival to those that express these antigens with low serum levels of CA 19-9 after surgery.

The other surprising finding in RTOG 9704 is the fact that 34% of patients were Lewis antigen negative, which is much higher than the 7% to 10% which is generally quoted in the literature.⁴ As discussed our article,² there was likely variability in the testing for Lewis antigen in the blood banks and laboratories of the enrolling institution. RTOG was not responsible for this testing and therefore could not oversee its quality control. Was this a missed opportunity? Probably. Additional examination of the relationship between Lewis antigen expression and CA 19-9 levels would have been valuable in patients with pancreatic cancer in a prospective fashion, especially in this large trial. However, in today's economic times when research funding has plateaued or diminished, it is challenging to obtain support for such projects.

AUTHORS' DISCLOSURES OF POTENTIAL CONFLICTS OF INTEREST

The author(s) indicated no potential conflicts of interest.

REFERENCES

1. Atkins CD: CA 19-9 and Lewis antigens in pancreatic cancer. J Clin Oncol 27:2572–2573, 2009.[Free Full Text]

2. Berger AC, Garcia M, Hoffman JP, et al: Postresection CA 19-9 predicts overall survival in pancreatic cancer patients treated with adjuvant chemoradiation: Prospective validation by RTOG 9704. J Clin Oncol 26:5918–5922, 2008.[Abstract/Free Full Text]

3. Tempero MA, Uchida E, Takasaki H, et al: Relationship of carbohydrage antigen 19-9 and Lewis antigens in pancreatic cancer. Cancer Res 47:5501–5503, 1987.[Abstract/Free Full Text]

4. Lamerz R: Role of tumour markers: Cytogenetics. Ann Oncol 10:145–149, 1999 (suppl 4.[CrossRef][Medline]

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• CA 19-9 and Lewis Antigens in Pancreatic Cancer
  Carl D. Atkins
  JCO 2009 27: 2572-2573 [Full Text]

This Article Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Email this article to a colleague Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Save to my personal folders Download to citation manager Rights & Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Berger, A. C. Articles by Willet, C. Search for Related Content PubMed PubMed Citation Articles by Berger, A. C. Articles by Willet, C. Related Articles Related Article Social Bookmarking                            What's this?