This study provides epidemiologic data from patients with CRC in Trinidad & Tobago that will be useful to guide screening programmes. It corrects the previous record suggesting that left-sided disease was more common in this nation. This data is in keeping with international data [3, 4, 5] documenting an increasing prevalence of right-sided CRC.
Caribbean countries have reported similar patterns of right-sided CRC predominance [6, 8, 9, 10, 11]. The prevalence of right sided lesions in Barbados is 44.3% as reported by Griffith et al [6]. In Jamaica, McFarlane et al [8] reported right sided lesions in 28.5% and in Martinique, Joachim et al [6] reported right sided lesions in 26.3% of patients. We found right-sided lesions in 42.7% of Trinidadian patients, which was unexpected as they approximated figures from Barbados, that ranks globally in the top ten nations for CRC incidence [1].
The only Caribbean study that suggested a left-sided prevalence was the previously cited study from Trinidad & Tobago [2] that examined 118 resected specimens. This study was flawed for two reasons: first, the authors assigned rectal primaries as left-sided lesions, contrary to most definitions. They also defined right-sided lesions as those ‘found in the ascending colon, including the caecum, and up to the proximal half of the transverse colon’. It has already been pointed out that this is not the accepted, standardized definition. The definition is important because left and right sided CRC have fundamentally different clinical behaviours [7]. Right sided lesions have a greater association with microsatellite instability [12], and poorer survival statistics [13]. For this reason, there is consensus on the definition of geographic origin of the primary [4, 5, 6, 7]. The standardized definition of a right-sided CRC is one that originates in the caecum, ascending colon, hepatic flexure and/or transverse colon, while a left-sided lesion is one that arises from the splenic flexure, descending and/or sigmoid colon [4, 5, 6, 7]. Rectal cancers are not included in the definition of laterality.
The high proportion of Afro-Caribbean patients (50.3%) was notable, since the population in Trinidad & Tobago is equally divided amongst Afro (40%) and Indio-Caribbean (40%) ethnicities [14]. But it was not unexpected since international data has shown that, compared to other ethnicities, blacks tend to have a higher incidence of CRC [15, 16], increased association with genetic mutations [12, 17], and a more aggressive disease course [12, 17, 18].
We also demonstrated that women were statistically more likely to develop right-sided CRCs than males. This pattern is similar to that reported in other countries [19, 20, 21, 22] and it has clinically significance since right-sided CRC have more aggressive behaviour and poorer survival statistics [12, 19, 20, 21, 22, 23].
Our study was limited by the unavailability of immunohistochemical and molecular predictive biomarkers for CRC. It is estimated that genetic factors such as mis-match repair gene mutations and MUTYH genes contribute to CRC incidence in up to one third of patients [12]. These markers were not universally available for evaluation in the present study.