Surgeons Find Higher Than Expected Rate of Aggressive Rectal Cancer in Younger Adults

Novel study finds signet cell histology is far more prevalent in rectal cancer patients under age 40

SAN FRANCISCO, Oct. 26, 2011 /PRNewswire-USNewswire/ -- University of Minnesota surgeons have confirmed a rising trend in rectal cancer in people age 40 and younger in recent years.  While a previous 2010 study in the journal CANCER also found a recent rise in adenocarcinoma of the rectum in younger patients, (1) the University of Minnesota surgeons report that their study is the first to identify a near fivefold increased risk of signet cell histology appearing in patients under age 40.  The investigators reported their findings at the 2011 Annual Clinical Congress of the American College of Surgeons.

The University of Minnesota team used the Surveillance, Epidemiology and End Results (SEER) national cancer registry, the largest cancer database in the United States.  They isolated the rectal adenocarcinoma cases in the SEER database and determined that signet cell histology, a unique type of cancer cell, was almost five times more prevalent in those under age 40 with rectal cancer than in older patients.  "The prevalence of signet cell histology in patients under age 40 was statistically significant at 4.63 percent vs. 0.78 percent in patients over 40," according to lead investigator Patrick S. Tawadros, MD, Ph.D., FRCSC.

Dr. Tawadros explained that signet cell histology is similar to the mucinous type of adenocarcinoma, in that both produce mucin, but "the main distinguishing feature of signet cell is a lack of cell-to-cell adhesion molecules," Dr. Tawadros said.  "As a result, these signet cells can migrate more freely and exhibit a more aggressive mode of spread."  Signet cell adenocarcinoma is typically diagnosed at a more advanced cancer stage, and this form of rectal cancer usually carries a worse prognosis than the mucinous and non-mucinous forms of rectal adenocarcinoma.

"While rectal cancer remains fairly uncommon in patients under 40, the rising trend combined with our novel finding that signet cell histology is found at a rate of almost one in 20 in this population is cause for attention," Dr. Tawadros said. "Clinicians need to be aware of this condition and carefully assess patients who present with any symptoms or signs that may be suggestive of rectal cancer."

While authors of other studies have stopped short of advocating for aggressive colonoscopy in this age group, some have said a less invasive diagnostic test, flexible sigmoidoscopy, may be warranted when rectal bleeding or other telltale signs of rectal cancer exist.  However, University of South Florida surgeons recently put the screening question forward in a Journal of the American College of Surgeons study, in which they specifically set out to determine if the recommended screening age for colorectal cancer should be lowered, noting that "the most significant increase in CRS has occurred in patients ages 40 to 44," and "many of these cancers would be missed with sigmoidoscopy."  They concluded that "consideration should be given for age-based colonoscopic screening beginning at age 40, an age at which the incidence mirrors other accepted screened cancers." (2)

While there is no clear consensus on lowering the recommended screening age for colon and rectal cancers, the University of Minnesota researchers are preparing to take the next step in their research.  They are seeking to determine if a genetic predisposition exists for signet cell adenocarcinoma of the rectum.  "There is rationale to hypothesize that a combination of genetic testing, family history, and potential associations with other cancers could help clinicians predict those at risk of developing this condition," Dr. Tawadros concluded.

Other investigators in the study were Ian M. Paquette, MD; Ann M. Hanly MD, MSc, FRCSI; Anders F. Mellgren, MD, Ph.D., FACS; David A. Rothenberger, MD, FACS; and Robert D. Madoff, MD, FACS.

(1)) Meyer, JE et al. "Increasing Incidence of Rectal Cancer in Patients Aged Younger Than 40 Years." Cancer 2010 Sep 15:4353-4358.
(2) Davis, DM et al. "Is It Time to Lower the Recommended Screening Age for Colorectal Cancer?" J Am Coll Surg. 2011 Sep:352-361.

SOURCE American College of Surgeons