Interval Colorectal Cancer Incidence Among Subjects Undergoing Multiple Rounds of Fecal Immunochemical Testing

Abstract

Background & aims: Among subjects screened for colorectal cancer (CRC) by the guaiac fecal occult blood test, interval cancers develop in 48% to 55% of the subjects. Data are limited on how many persons screened by fecal immunochemical tests (FIT), over multiple rounds, develop interval cancers. In the Netherlands, a pilot FIT-based biennial CRC screening program was conducted between 2006 and 2014. We collected and analyzed data from the program on CRCs detected during screening (SD-CRC) and CRCs not detected within the screening program (non-SD-CRC; such as FIT interval cancers, colonoscopy interval cancers, and cancer in nonparticipants).

Methods: Screenees with a negative FIT result received a letter explaining that no blood had been detected in the stool sample and were re-invited, if eligible, for screening biennially. Screenees with a positive FIT result (hemoglobin concentration of 10 μg Hb/g feces) were invited for consultation and scheduled for colonoscopy; results were collected. After the fourth round of FIT screening, the cohort was linked to the Netherlands Cancer Registry, through March 31, 2015; participant characteristics, data on tumor stage, location (at time of resection), and survival status were collected for all identified CRC cases. A reference group comprised all persons with CRC diagnosed in the Netherlands general population during the same period, in the same age range (50-76 years), who had not been offered CRC screening. The median time between invitations (2.37 years) was used as a cutoff to categorize participants within the FIT interval cancer category. We compared participant characteristics, tumor characteristics, and mortality among subjects with SD-CRC and with non-SD-CRC.

Results: A total of 27,304 eligible individuals were invited for FIT screening, of whom 18,716 (69%) participated at least once. Of these, 3005 (16%) had a positive result from the FIT in 1 of the 4 screening rounds. In total, CRC was detected in 261 participants: 116 SD-CRCs and 145 non-SD-CRCs (27 FIT interval cancers, 9 colonoscopy interval cancers, and 109 CRCs in nonparticipants). The FIT interval cancer proportion after 3 completed screening rounds was 23%. Participants with SD-CRC had more early-stage tumors than participants with non-SD-CRCs (P < .001). Of persons with SD-CRC and FIT interval cancers, significantly higher proportions survived (89% and 81%, respectively) compared with persons with colonoscopy interval cancers (44% survival) and nonparticipants with CRC (60% survival) (P < .001).

Conclusions: In an analysis of data from a pilot FIT-based biennial screening program, we found that among persons screened by FIT, 23% developed FIT interval cancer. FIT therefore detects CRC with 77% sensitivity. The proportion of FIT interval cancers in FIT screening appears to be lower than that with guaiac fecal occult blood testing. Clinical trial registry: yes, www.trialregister.nl, trial number: NTR5385.

Keywords: Colon Cancer; Early Detection; Tumor; fFOBT.