Clinicopathological differences and correlations between right and left colon cancer

The differences in histopathology and molecular biology between right colon cancer (RCC) and left colon cancer (LCC) were first reported in the literature by Bufill in 1990. Since then, a large number of studies have confirmed their differences in epidemiology, clinical presentation, comorbidities and biological behaviours, which may be related to the difference in prognosis and overall survival (OS) between the two groups.

To investigate statistically significant differences between Greek patients with LCC and RCC.

The present observational study included 144 patients diagnosed with colon cancer of any stage who received chemotherapy in a Greek tertiary oncology hospital during a 2.5-year period. Clinical information, comorbidities, histopathologic characteristics and molecular biomarkers were collected from the patients' medical records retrospectively, while administered chemotherapy regimens, targeted agents, progression-free survival (PFS) periods with first- and second-line chemotherapy and OS were recorded retroactively and prospectively. Data analysis was performed with the SPSS statistical package.

Eighty-six males and 58 females participated in the study. One hundred (69.4%) patients had a primary lesion in the left colon, and 44 (30.6%) patients had a primary lesion in the right colon. Patients with RCC were more likely to display anaemia than patients with LCC [odds ratio (OR) = 3.09], while LCC patients were more likely to develop rectal bleeding (OR = 3.37) and a feeling of incomplete evacuation (OR = 2.78) than RCC patients. Considering comorbidities, RCC patients were more likely to suffer from diabetes (OR = 3.31) and coronary artery disease (P = 0.056) than LCC patients. The mucinous differentiation rate was higher in the right-sided group than in the left-sided group (OR = 4.49), as was the number of infiltrated lymph nodes (P = 0.039), while the percentage of high-grade differentiation was higher in the group of patients with left-sided colon cancer than in RCC patients (OR = 2.78). RAS wild-type patients who received anti-epidermal growth factor receptor (EGFR): Treatment experienced greater benefit (PFS: 16.5 mo) than those who received anti-vascular endothelial growth factor treatment (PFS: 13.7 mo) (P = 0.05), while among RAS wild-type patients who received anti-EGFR treatment, LCC patients experienced greater benefit (PFS: 15.8 mo) than the RCC subgroup (PFS: 5.5 mo) in the first-line chemotherapy setting (P = 0.034). BRAF-mutant patients had shorter PFS (9.3 mo) than BRAF wild-type patients (14.5 mo) (P = 0.033). RCC patients showed a shorter tumour recurrence period (7.7 mo) than those with LCC (14.5 mo) (P < 0.001), as well as shorter (OS) (58.4 mo for RCC patients; 82.4 mo for LCC patients) (P = 0.018).

RCC patients present more comorbidities, worse histological and molecular characteristics and a consequently higher probability of tumour recurrence, poor response to targeted therapy and shorter OS than LCC patients.