Distribution Patterns of Colorectal Cancer and its Precursors

Abstract

Growing evidence shows that not only colorectal cancer (CRC) incidence but also its distribution patterns are changing.  It is important to understand these changes to guide CRC screening, management, and public health strategies. We retrospectively analyzed the database of Miraca Life Sciences Research Institute for a one-year period (January 1 to December 31, 2009).  We extracted all patients’ records with a diagnosis of CRC signed by all Miraca pathologists and compared with patients with a diagnosis of tubular adenoma (TA), sessile serrated adenoma/polyp (SSA/P), and traditional serrated adenoma (TSA) signed by a single GI pathologist for diagnosis consistency during the same period.  Patients’ age, gender, and anatomic locations were analyzed and mapped in the study.  A total of 1,757 patients with CRC, 1,341 with TA, 199 with SSA/P and 36 TSA were studied.  The distribution patterns of CRC and TSA showed a significant left-sided colon predominance (62.9% of CRC, p < 0.001; 76.3% of TSA, p = 0.013), especially in the sigmoid and rectum regions. In contrast, SSA/P showed a significant right-sided distribution pattern (67.9%, p < 0.001) and TA showed a slightly predominant toward the right-sided colon (53.1%, p = 0.041).  Although the distribution pattern of CRC was left-sided predominant, it shifted toward right-sided colon among patients with advancing age and being female gender.  This study indicates that dynamic shift of CRC from left-sided colon toward right-sidedness was largely due to patients’ advancing age and being female gender.  The right-sided predominant distribution patterns of SSA/P might play an important role in the increased risk of right-sided CRC.  Therefore, it is important to take extra effort to examine right-sided colon endoscopically in high risk patients.