Intermediate-onset colorectal cancer: a clinical and familial boundary between both early and late-onset colorectal cancer

Comparative studies of colorectal cancer (CRC) according to the age of onset
have found differences between early-onset CRC (EOCRC) and late-onset CRC
(LOCRC). Using this as a starting point, we wished to determine whether intermediateonset
CRC (IOCRC) might also be considered as an independent group within CRC.
We performed a retrospective comparative study of the clinicopathological and familial
features, as well as of the symptoms and their duration, of a total of 272 subjects
diagnosed with CRC classified into three groups according to the age-of-onset (98
EOCRC, 83 IOCRC and 91 LOCRC). The results show that from a clinicopathological
point of view, IOCRC shared certain features with EOCRC (gender, prognosis), and
with LOCRC (multiple primary CRCs), whereas it also had characteristics that were
specific for IOCRC (mean number of associated polyps). A gradual progression was
observed from EOCRC to LOCRC from a greater family aggregation to sporadic cases,
in parallel with a change of Lynch Syndrome cases to the sporadic microsatellite
instability pathway, with the IOCRC being a boundary group that is more related to
EOCRC. With respect to symptoms, duration and correlation with stages, IOCRC
appeared more similar to EOCRC. Clinically, IOCRC behaves as a transitional group
between EOCRC and LOCRC, with features in common with both groups, but also
with IOCRC-specific features. Excluding cases with familial cancer history, the
awareness for EOCRC diagnosis should be extended to IOCRC.