Reply: Immortal time bias in a retrospective study examining colorectal cancer mortality according to adherence to colonoscopy

We appreciate Dr Winters and Dr Ford’s letter1 for the opportunity to clarify the role of immortal time bias that in the authors’ opinion may have affected the results of our previous article.2 Several sensitivity analyses were conducted to examine whether changing the time window at risk after positive faecal immunochemical test (FIT) affected estimated risks, but no significant differences were observed. There are two main reasons for this. The first is intrinsically related to colorectal cancer (CRC) screening that in most cases detects initial lesions.3 4 Given progression to CRC is slow, dying within the first months of a FIT positive test from a most probably asymptomatic CRC is highly unlikely. In fact, out of 505 overall CRC deaths, only 3 (0.6%) occurred in the first month, 9 (1.8%) up to the second month, 31 (6.1%) in the first 6 months...

Source: Gut - October 6, 2023 Category: Gastroenterology Authors: Zorzi, M., Battagello, J., Barbiellini Amidei, C. Tags: Gut PostScript Source Type: research