A study in the April issue of Radiology has found that one out of every 200 asymptomatic people who have been screened with virtual colonoscopy has a clinically unsuspected malignant cancer, and that half of those cancers were located outside of the colon.
"We are finding that virtual colonoscopy screening actually identifies more unsuspected cancers outside of the colon than within it," said lead author Perry J. Pickhardt, MD, professor of radiology and chief of gastroenterologic imaging, at the University of Wisconsin School of Medicine & Public Health in Madison. "As with asymptomatic colorectal cancers identified by virtual colonoscopy screening, these cancers are often detected at an early, curable stage."
Pickhardt and his colleagues reviewed 10,286 patients who underwent CT colonography (CTC) screening from April 2004 through March 2008. Prospective evaluation for both colorectal and extracolonic disease was performed by one of seven experienced radiologists immediately after the exam.
For all patients with a pathologically proved unsuspected cancer detected at CTC, additional diagnostic work-up, method of tissue diagnosis, clinical tumor stage, mode of therapy and subsequent clinical outcome (assessed from clinical oncology follow-up notes, medical records review and direct provider feedback) were assessed and tabulated. For statistical analysis, the researchers made primary comparisons between patients with unsuspected cancers detected at CTC and the remainder of the screening population.
After the clinical work-up of newly detected findings at screening CTC, unsuspected malignancy was confirmed in 58 subjects, including 22 cases of colorectal cancer and 36 cases of extracolonic cancer.
The mean age of the 58 patients with unsuspected cancer was 60.8 years, which was one year older on average than those without cancer. Women made up a slight majority (56.9 percent) of the unsuspected cancer cases. Cancers in 53.4 percent of patients were stage 1 or localized cancers.
"Although extracolonic evaluation at screening CT colonography does carry some disadvantages, such as patient anxiety, inconvenience or the potential for benign biopsy, our results suggest that early detection of asymptomatic extracolonic cancer represents an additional benefit of screening CT colonography that is not available with optical colonoscopy," Pickhardt said.