1100 Incidence of Advanced Neoplasia in Asymptomatic Patients With Diminutive Adenomatous Polyps Detected and Untreated At Initial Screening Colonoscopy

Abstract

1100 Incidence of Advanced Neoplasia in Asymptomatic Patients With Diminutive Adenomatous Polyps Detected and Untreated At Initial Screening Colonoscopy Yosuke Otake, Yasuo Kakugawa, Takahisa Matsuda, Chihiro Tsunoda, Yutaka Saito, Yukio Muramatsu, Noriyuki Moriyama Endoscopy division, National Cancer Center Hospital, Tsukiji, Japan; Screening Technology and Development Division, National Cancer Center, Tsukiji, Japan Background and Aim: Effectiveness of colonoscopic removal of adenomatous polyps for prevention of colorectal cancer has been reported and various intervals suggested between colonoscopies after removal of such adenomatous polyps. It is still unclear, however, whether removal of even diminutive adenomatous polyps is necessary. We investigated the incidence of advanced neoplasia in an asymptomatic group in which diminutive adenomatous polyps were detected, but not removed at initial screening colonoscopy and then compared such incidence to the incidence for an asymptomatic group in which no adenomatous polyps were detected at initial screening colonoscopy. Method: We recommend repeat colonoscopy within five years for asymptomatic patients in whom diminutive adenomatous polyps 5mm are detected, but not removed at initial screening colonoscopy as well as for asymptomatic patients without any adenomatous polyps. As for patients in whom larger adenomatous polyps 5mm or cancers are detected, we recommend appropriate therapy. We retrospectively investigated the cumulative incidence of index lesions (ILs) following initial screening colonoscopy in two groups of patients: those without any adenomatous polyps (Group A); and those with adenomatous polyps 5mm (Group B). ILs following initial screening colonoscopy were defined as adenomas 10mm, high-grade dysplasias and cancers. Results: We studied a total of 2,270 asymptomatic patients (1,713 in Group A and 557 in Group B) with a total of 806 diminutive adenomatous polyps detected at initial screening colonoscopy in Group B (1.45 polyps per patient). Median intervals were 59 months and 53 months and cumulative incidences of ILs were 1.0% and 2.2% in Groups A and B, respectively. Cumulative incidence of ILs in Group B was significantly higher compared to Group A (p 0.034) although all 12 detected ILs (two adenomas 10mm, six high-grade dysplasias, three intramucosal cancers and one submucosal cancer with slight invasion) in Group B were successfully treated by endoscopic resection. There were no advanced cancers detected in Group B, but two advanced cancers were detected at follow-up colonoscopies in Group A (not significant). Conclusion: Patients with diminutive adenomatous polyps that were not removed had a significantly higher risk of advanced neoplasia in comparison to patients without any such adenomatous polyps, but invasive cancers requiring surgery or chemotherapy were not detected by followup colonoscopy. It seems unnecessary to remove diminutive adenomatous polyps detected during initial screening colonoscopy of asymptomatic patients, therefore, provided such patients undergo recommended follow-up colonoscopy.