‘Flat’ Colon Lesions Relatively Common, Associated With Colorectal Cancer

03/04/08  Chicago

Nationally renowned colorectal cancer screening expert at Oregon Health & Science University explains, in accompanying editorial, that more study is needed to determine whether intensive colonoscopies can better detect these life-threatening lesions

Flat, non-polypoid colorectal neoplasms (NP-CRNs), which may be difficult to detect, appear to be relatively common and may have a greater association with cancer compared with the more routinely diagnosed type of colorectal polyps, according to a study in the March 5 issue of JAMA, the Journal of the American Medical Association.

Colorectal cancer is the second leading cause of cancer death in the United States. Prevention has focused on the detection and removal of polypoid (resembling a polyp) neoplasms (a new and abnormal growth). Recent studies, however, have demonstrated that colorectal cancer can also arise from NP-CRNs.

“Nonpolypoid colorectal neoplasms are more difficult to detect by colonoscopy or computed tomography colonography because the subtle findings can be difficult to distinguish from those of normal mucosa [membrane]. As compared with surrounding normal mucosa, NP-CRNs appear to be slightly elevated, completely flat, or slightly depressed,” the authors write. Data are limited on the significance of NP-CRNs.

Roy M. Soetikno, M.D., M.S., and colleagues with the Veterans Affairs Palo Alto Health Care System, Palo Alto, Calif., examined data from a group of 1,819 patients undergoing elective colonoscopy to estimate the prevalence of NP-CRNs and to characterize the association of NP-CRNs with colorectal cancer.

The overall prevalence of NP-CRNs was 9.35 percent (n = 170). The prevalence of NP-CRNs in the subpopulations for screening, surveillance, and symptoms was 5.84 percent, 15.44 percent, and 6.01 percent, respectively. The overall prevalence of NP-CRNs with cancer that had not spread or had spread in tissue beneath the mucous membrane was 0.82 percent; in the screening population, the prevalence was 0.32 percent. Overall, NP-CRNs were nearly 10 times more likely to contain cancerous tissue than polypoid lesions, irrespective of the size.

The positive size-adjusted association of NP-CRNs with cancer that had not spread or had spread in tissue beneath the mucous membrane was also observed in subpopulations for screening and surveillance. The depressed type of NP-CRNs had the highest risk (33 percent). Nonpolypoid colorectal neoplasms containing cancer were smaller in diameter as compared with the polypoid ones.

“In conclusion, in this population of patients at a single Veterans Affairs hospital, NP-CRNs were a relatively common finding during colonoscopy. They were more likely to contain carcinoma compared with polypoid neoplasms, independent of lesion size. Recent studies have pointed out differences in the genetic mechanisms underlying nonpolypoid and polypoid colorectal neoplasms. Future studies on NP-CRNs should further evaluate whether the diagnosis and removal of NP-CRNs has any effect on the prevention and mortality of colorectal cancer and particularly focus on their genetic and protein abnormalities,” the authors write.

Editorial: Nonpolypoid Colorectal Neoplasia in the United States

In an accompanying editorial, David Lieberman, M.D., professor of medicine, head of the Division of Gastroenterology, Oregon Health & Science University School of Medicine, Portland Veterans Affairs Medical Center; member, OHSU Cancer Institute; and co-director, OHSU Digestive Health Center, comments on the findings of Soetikno and colleagues.

“Nonpolypoid colorectal neoplasms may be biologically distinct from polypoid lesions and appear to be more likely to harbor malignant features. Detection and complete removal at colonoscopy may be challenging. The current study emphasizes the importance of quality in the performance of colonoscopy,” he writes. “The optimal methods for enhancing colonoscopic imaging of NP-CRNs are uncertain. … Additional studies are needed to determine whether imaging modalities such as computed tomography colonography will be able to detect NP-CRNs. Finally, longitudinal studies are needed to determine whether patients with NP-CRNs require more intensive colonoscopic surveillance compared with patients with polypoid lesions of similar size and histology.”
(JAMA. 2008;299[9]:1068-1069.)

Editor’s Note: Please see the article for additional information, including financial disclosures, funding and support, etc.

About the OHSU Cancer Institute
The OHSU Cancer Institute is the only National Cancer Institute-designated center between Sacramento and Seattle. It comprises some 120 clinical researchers, basic scientists and population scientists who work together to translate scientific discoveries into longer and better lives for Oregon's cancer patients. In the lab, basic scientists examine cancer cells and normal cells to uncover molecular abnormalities that cause the disease. This basic science informs more than 200 clinical trials conducted at the OHSU Cancer Institute.

About OHSU
Oregon Health & Science University is the state’s only health and research university and Oregon’s only academic health center. OHSU is Portland's largest employer and the fourth largest in Oregon (excluding government), with 12,400 employees. OHSU's size contributes to its ability to provide many services and community support activities not found anywhere else in the state. It serves patients from every corner of the state, and is a conduit for learning for more than 3,400 students and trainees. OHSU is the source of more than 200 community outreach programs that bring health and education services to every county in the state.