Objective This study aims to elucidate the association between the clinical characteristics of post-colonoscopy colorectal cancer (PCCRC) and quality indicators (QIs) of colonoscopy. Methods Patients with PCCRC who underwent total colonoscopy (TCS) and were histologically diagnosed with adenocarcinoma within six months to five years of the last examination were included in this study. PCCRC and normally detected cancer (NDC) identified within the same period were compared in terms of their clinicopathological characteristics. Furthermore, the QIs at PCCRC detection were compared to those at the last examination. Results Patients with PCCRC had a significantly higher rate of colon surgery history than those with NDC (PCCRC: 25/76, 32.9%; NDC: 31/1,437, 2.2%; p<0.001), but the invasion depth in these patients was significantly shallower (PCCRC: ≤Tis/≥T1, 37/39; NDC: ≤Tis/≥T1, 416/1,021; p<0.001). Among patients with PCCRC, the T1b group had significantly more non-polypoid growth (NPG)-type cases than PG-type CRC cases (p=0.018). The adenoma detection rate (ADR) of colonoscopists performing TCS was 30.2-52.8%. Furthermore, the ADR of colonoscopists at the time of PCCRC detection (36.7%±5.9%) was significantly higher than that of colonoscopists who performed the last examination (34.9%±4.4%; p=0.034). The withdrawal time for negative colonoscopy (WT-NC) at detection was significantly longer than that at the last examination (at detection: 494.3±253.8 s; at last examination: 579.5±243.6 s; p=0.010). Conclusion Given that these PCCRC cases were post-colon surgery cases, had a long WT-NC, and were detected by colonoscopists with a high ADR, most cases showed lesions that were missed during the previous colonoscopy. Caution should be practiced in order to avoid missing flat, NPG-type tumors.
Keywords: adenoma detection rate; interval cancer; polypoid growth; post-colonoscopy colorectal cancer; quality indicator.