Affiliations of authors: J. Jen, Laboratory of Population Genetics, Center for Cancer Research, National Cancer Institute, Bethesda, MD; B. Vogelstein, The Howard Hughes Medical Institute and The Sidney Kimmel Comprehensive Cancer Center, The Johns Hopkins University School of Medicine, Baltimore, MD.
Correspondence to: Jin Jen, Ph.D., Laboratory of Population Genetics, Center for Cancer Research, National Cancer Institute, Bldg. 41, Rm. D702, 41 Library Dr., Bethesda, MD 20892 (e-mail: jenj{at}mail.nih.gov).
Frattini et al., describe in their correspondence that only distal colonic cancers could be detected from stool samples by using K-Ras gene mutations as a molecular marker. This observation supports our original paper (1) in which K-Ras gene mutations were only detectable in the stools from approximately 50% of tumors that had a mutation, and all detected tumors were originated in the distal colon. Although several possibilities were suggested, the exact mechanism of this lower sensitivity for K-Ras has not been examined directly. We believe the clearest conclusion from our study and from Frattini et al. is that a K-Ras gene mutation is not a reliable marker for colorectal cancer detection. By contrast, TP53 and APC genes (1,2), as well as BAT26 (3), are better markers because they provide highly sensitive and specific molecular detection of colorectal neoplasms, regardless of tumor stage and location.
REFERENCES
1 Dong SM, Traverso G, Johnson C, Geng L, Favis R, Boynton K, et al. Detecting colorectal cancer in stool with the use of multiple genetic targets. J Natl Cancer Inst
2001;93:85865.
2 Traverso G, Shuber A, Levin B, Johnson C, Olsson L, Schoetz DJ, et al. Detection of APC mutations in fecal DNA from patients with colorectal tumors. N Engl J Med
2002;346:31120.
3 Traverso G, Shuber A, Olsson L, Levin B, Johnson C, Hamilton SR, et al. Detection of proximal colorectal cancers through analysis of faecal DNA. Lancet 2002;359:4034.[CrossRef][Medline]
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