Survival Trends of Right- And Left-Sided Colon Cancer across Four Decades: A Norwegian Population-Based Study

Abstract

Background: Patients with right-sided colon cancer (RCC) and 0.90–1.02; P ¼ 0.179). In 2007 to 2016, LCC had significantly left-sided colon cancer (LCC) differ clinically and molecularly. The better OS (HR, 0.84; 95% CI, 0.80–0.87; P < 0.001) and RS (eHR, main objective was to investigate stage-stratified survival and 0.76; 95% CI, 0.72–0.81; P < 0.001) compared with RCC. The recurrence of RCC and LCC across four 10-year periods. gradually diverging and significantly favorable prognosis for LCC Methods: Patients diagnosed from 1977 to 2016 with colon was evident for distant disease across all time periods and for regional adenocarcinoma were included from the Cancer Registry of Nor-disease from 2007 onward. There was no difference in RFS between way. Primary tumor location (PTL) was defined as RCC if proximal LCC and RCC in patients less than 75 years during 2007 to 2016 (HR, and LCC if distal to the splenic flexure. Multivariable regressions 0.99; 95% CI, 0.91–1.08; P ¼ 0.819); however, SAR was significantly were used to estimate HRs for overall survival (OS), recurrence-free better for LCC (HR, 0.61; 95% CI, 0.53–0.71; P < 0.001). survival (RFS), survival after recurrence (SAR), and excess HRs Conclusions: A gradually diverging and increasingly favorable (eHR) for relative survival (RS). prognosis was observed for patients with LCC with advanced Results: 72,224 patients were eligible for analyses [55.1% (n ¼ disease over the past four decades. 39,769/72,224) had RCC]. In 1977 to 1986, there was no differ-Impact: Current PTL survival disparities stress the need for ence between LCC and RCC in OS [HR, 1.01; 95% confidence further exploring targetable molecular subgroups across and within interval (CI), 0.97–1.06; P ¼ 0.581] or RS (eHR, 0.96; 95% CI, different PTLs to further improve patient outcomes.