Colorectal two-week wait service and quantitative FIT: it's not just about colon cancer

The aim of this study was to assess faecal immunochemical test (FIT) negativity in terms of its effect on cancer risk in the local symptomatic two-week wait (2WW) population. FIT was introduced to the colorectal 2WW pathway at the start of the pandemic. This study analyses the FIT-negative (<10µg Hb/g) cohort and calculates the relative risk and odds ratio associated with a negative FIT test.

FIT tests were sent to symptomatic 2WW patients without rectal bleeding, iron-deficient anaemia or palpable mass. Where FIT was <10µg Hb/g investigations were moved to a radiology protocol.

The test return rate was 91% with a FIT-negative (<10µg Hb/g) rate of 82%. The FIT-negative group in the symptomatic referral pathway in Cornwall have a low (1.4%) risk of colon cancer but a significant risk (6.6%) when all cancer types are considered. The impact of a negative quantitative FIT changes the odds ratio of a patient having a luminal cancer by 0.26. The odds ratio for 'all cancer' risk was affected by 0.83.

A negative FIT test within the local NG12 symptomatic patient group signifies a low risk of colon cancer and identifies patients who can be initially investigated with cross-sectional imaging. However, when all cancer types are considered, cancer prevalence in this group remains above 6%. In relative risk terms a negative FIT represents a small change in overall risk and this patient group still qualify for investigation through 2WW pathways.