Results of a French screening campaign comparing clinical and molecular characteristics of interval colorectal cancers to cancers detected using a guaiac test.

Few studies have analyzed the biological characteristics of interval colorectal cancers (CRC) during a screening campaign. We included 98 patients of whom 46 had a screened cancer (SCG) and 52 an interval cancer (ICG). Microsatellite instability and gene mutation profiling were performed in 86 and 55 patients, respectively. ICG were diagnosed with more advanced diseases. A time interval between last negative test and CRC diagnosis (TIg2D) ≥ 18 months, in the ICG, was associated with an increased risk of metastasis at diagnosis. Old age, male gender, rectal cancer and TIg2D ≥ 18 months were associated with a worse outcome in ICG. Interval cancers remained associated with a worse survival in an adjusted Cox model. There was no significant difference in terms of mutation frequency between SCG and ICG. However, APC / CTNNB1 mutations were less frequent in rectum cancers of ICG. Furthermore, KRAS activating mutations were less frequent in the ICG when age at diagnosis was below 65 years or if patients had colon cancer. When compared to the SCG, the survival of ICG was significantly worse in patients with wild-type KRAS. These results suggest that men and elderly subjects could benefit from annual screening. Patients with rectum cancer and wild-type APC/CTNNB1/KRAS should be considered as high-risk subjects.