Proven: Colorectal Screening Cuts Deaths 50%

July 1, 1996

SAN FRANCISCO--Average-risk individuals over age 50 can be effectively screened for colorectal cancer by use of annual fecal occult blood testing and sigmoidoscopy every 5 years, John H. Bond, MD, said at a press conference during Digestive Disease Week (DDW).

SAN FRANCISCO--Average-risk individuals over age 50 can be effectivelyscreened for colorectal cancer by use of annual fecal occult bloodtesting and sigmoidoscopy every 5 years, John H. Bond, MD, saidat a press conference during Digestive Disease Week (DDW).

An educational campaign launched at the meeting is designed toraise public awareness about the importance of screening and spurprimary care physicians to suggest colorectal screening to appropriatepatients.

"Two large prospective randomized trials performed at myinstitution, the University of Minnesota, and at Memorial Sloan-KetteringCancer Center, have now reported definitive end point resultsshowing that this form of cancer screening will reduce colorectalcancer deaths by 50%," Dr. Bond said.

Dr. Bond countered the critics of such screening who point outits limitations. "There are some limitations with any simplescreening test, and further research is needed in some areas,but I feel the critics have almost gone too far and are interferingwith the implementation of the tests today," he said.

Critics have argued that colorectal screening is not sensitiveenough in detecting cancers, but Dr. Bond said that the two largeUS studies have shown that very few colorectal cancers are missedwith the type of screening that is being recommended. "Sensitivitywas 92% in the Minnesota trial, meaning that this form of screeningpicked up 92 of 100 cancers at an early asymptomatic stage,"he said.

Others have argued that screening should not be implemented untilresults from the three ongoing European studies are available,but Dr. Bond pointed out that all of the preliminary data fromthese studies are "absolutely consistent" in showingreduced mortality, detection at an earlier stage, and longer survivalafter surgery in screened populations.

"There just isn't likely to be any new substantial informationthat will alter these recommendations at least for the next 10to 20 years until we have maybe some new way of screening forcolorectal cancer," he said.

Dr. Bond emphasized that last December, the US Preventive ServicesTask Force for the first time recommended that the entire US populationover age 50 be screened for colorectal cancer with annual fecaloccult blood testing and sigmoidoscopy every 5 years, "andthat same recommendation has been made by all of the GI societiesas well as the American Cancer Society, the World Health Organization,and other groups."

To facilitate implementation of the screening recommendation,the GI societies represented at DDW have launched the DigestiveHealth Initiative Colon Cancer Campaign, which will use mediaresources and written materials to educate the general publicas well as primary care physicians. Dr. Bond and Dr. Bernard Levinof the M.D. Anderson Cancer Center are codirectors of the campaign.

Importance of Family History

Also at the press conference, Ann Zauber, PhD, with the NationalPolyp Study, a collaborative effort headquartered at MemorialSloan-Kettering, described how the results of studies on familialcolorectal cancer risk are being implemented into clinical practice.

The National Polyp Study has focused on patients newly diagnosedwith adeno-mas (polyps), the precursor lesions for colorectalcancer. "We have just published data to show that close relativesof patients diagnosed with an adenoma, just like close relativesof patients with colo-rectal cancer, have almost a twofold increasedrisk of developing colorectal cancer," Dr. Zauber said.

In addition, the study found the same characteristics for increasedrisk with both colorectal cancer and adenoma families: The youngerthe age at which the ade-noma or cancer patient is diagnosed,the higher the risk for colorectal cancer in the family members.Also, if additional family members are affected, the remainingfamily members have a higher risk.

The American Cancer Society is now recommending screening withcolonos-copy for close relatives of patients with colorectal cancerdiagnosed at a young age, and, based on the new findings, Dr.Zauber's group strongly suggests that family members of adenomapatients diagnosed at a young age should also undergo screeningcolonoscopy.

The National Polyp Study showed that in newly diagnosed polyppatients, colonoscopy and removal of all polyps led to a 76% to90% reduction in colorec-tal cancer incidence, and this findingsuggests that colonoscopy screening should also reduce the colorectalcancer incidence in the relatives of these patients.

The study also found that it is safe to wait 3 years before thenext surveillance colonoscopy. Although more polyps were foundin those screened twice (at 1 year and 3 years), outcome was notaffected, she said, because the number of polyps with advancedpathology was the same (3%) in those screened at 3 years and thosescreened at 1 and 3 years.

With 6-year follow-up of these polyp patients who underwent colonoscopy,only five colorectal cancers have been found, and all were asymptomaticearly-stage disease.

Dr. Zauber pointed out that in the general population, at least20 colorectal cancers would have been expected, and in a polyp-bearingcohort that did not have intervention, 43 to 48 colon cancerswould have been predicted.

Colon Cancer Prevention Program

Memorial Sloan-Kettering's Colon Cancer Prevention Program isnow in its second year, Dr. Zauber said. In this program, familyhistory is incorporated as a tool to manage the colorectal canceror adenoma patient and make recommendations to family members.

"All patients are asked to complete a family history questionnaire,which is computer scanned into a database. The database then generatesa pedigree and a risk algorithm showing an individual patient'srisk for colorectal cancer or other cancers such as breast andendometrial cancer," Dr. Zauber said.

The pedigree and risk algorithm are then reviewed by a GeneticsReview Committee, which includes a gastroenterologist as wellas genetic counselors. Patients found to have a high componentof familial risk are referred for genetic counseling and potentialgenetic testing, while those at more intermediate risk are givena schedule for follow-up visits.

At the AUA meeting, Dr. Ira Breite gave a preliminary report onpolyp and colorectal cancer rates in 42 high-risk patients inthe program who underwent a total of 150 follow-up colonoscopies(an average 7 years of follow-up).

One cancer was found, for an incidence rate of 3.4/1,000 personyears, a finding similar to that of a Finnish study of patientswith hereditary nonpolyposis colon cancer (HNPCC) (4.9/1,000 personyears with screening vs 12.5/1,000 persons years without screening)and similar to that of the unscreened general population basedon SEER data (2.5/1,000 person years).

Eight polyps with advanced pathology were seen (27/1,000 personyears), which was higher than that seen in the National PolypStudy cohort (5/1,000 person years).

Thus, Dr. Breite concluded that patients with a high familialrisk of colorectal cancer receiving colonoscopy screening haverates of cancer similar to that of the unscreened general population,and that the findings support the Finnish study results showingthat screening leads to a reduction in colorectal cancer incidenceand mortality in high-risk families.