BOSTON — The debut of virtual colonoscopy as a mainstream option for colorectal cancer screening may be just months away, experts said at an international symposium on virtual colonoscopy sponsored by Boston University.
The much-anticipated results of the American College of Radiology Imaging Network's (ACRIN) national trial, are expected to be announced by late March 2007. The results are expected to show virtual colonoscopy (VC), also known as CT colonography, in a favorable light in comparison with conventional optical colonoscopy (OC), said one of the investigators, Dr. Judy Yee of the University of California, San Francisco.
The American Cancer Society expects to announce its updated colorectal cancer screening guidelines at about the same time, said Robert Smith, Ph.D., the society's director of cancer screening.
To date, the ACRIN trial has enrolled 2,468 of the 2,607 subjects needed to complete its comparison of both screening modalities, and the trial is scheduled to conclude in late November, said Dr. Yee.
“Where will the results fall?” she asked. In terms of the three most important multicenter trials comparing VC and OC, the excellent performance of VC in the landmark Pickhardt trial (New Engl. J. Med. 2003;349:2191–2200) was not replicated in the two more recent trials (JAMA 2004;291:1713–19, and Lancet 2005;365:305–11), Dr. Yee said.
“I don't think I am going out on a limb by saying the ACRIN results will fall right between,” she said. “I don't think the ACRIN trial will be able to achieve the 92% sensitivity [for VC] seen in the Pickhardt trial, but taking an educated guess I would say that sensitivity will fall maybe somewhere between 80% and 90%.”
Results like that would launch VC into the mainstream, predicted Dr. Joseph Ferrucci of Boston University. “We hope they will be the data that will be the final tipping point for the American Cancer Society to amend its guidelines to include VC,” he said in an interview.
Dr. Smith agreed that the ACRIN trial results will be important, but he would not comment on how they would influence the American Cancer Society's guidelines.
“I can't tell you whether we are going to wait [for the ACRIN results] or not,” he said in an interview. “We know the ACRIN timetable, and we are working on our guidelines now. If we are not done by the time the ACRIN results are out, we will most certainly want to see them at the earliest opportunity. We live in an electronic age, which means our guidelines process is always active. The potential is always there to adjust the guidelines in very short order if necessary.”
Recognition by the American Cancer Society of VC's strength as a colorectal cancer screening tool would likely carry it over the threshold toward full public and medical acceptance, said Dr. Perry Pickhardt of the University of Wisconsin, Madison, principal investigator of the 2003 landmark trial.
“This is an exciting time for VC as we move from validation into implementation,” said Dr. Pickhardt, adding that the next step needs to be acceptance by third-party payers. “We are treading water now waiting for widespread reimbursement.”
Dr. Smith agreed that the reaction of the American Cancer Society to the ACRIN results will be important. If VC is added to the society's guidelines, it is reasonable to expect a resulting improvement in competence among those who perform the test, greater overall investment in the approach, and greater public awareness, he said.
The end result will hopefully be better patient compliance with screening, Dr. Pickhardt said. “Currently, more than 40 million adults over the age of 50 are not being screened,” he said.