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J BUON. 2019 Mar-Apr;24(2):479-487.

The impact of primary tumor localization on survival and treatment outcomes in patients with metastatic colorectal cancer-a multicenter study.

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Van Education and Research Hospital, Department of Medical Oncology, Van, Turkey.



To investigate the effects of sidedness on survival and treatment outcomes in patients with metastatic colorectal cancer (mCRC), since the accumulated data have increasingly reported that patient with right-sided mCRC are found to be associated with worse overall survival (OS) and poor response to anti-epidermal growth factor receptor (anti-EGFR) agents.


This was a multi-center retrospective analysis of 177 patients with mCRC, who were treated and followed between 2014 and 2018 in different parts of Turkey. Patients were divided into 2 groups according to the primary tumor localization as right or left colon cancer. Clinical and demographic characteristics, treatment outcomes, and survival were analyzed to determine whether there was any association with tumor localization.


There were 53 (30%) patients with mCRC in the right group and 124 (70%) in the left group, with no difference between the groups in terms of clinical and demographic characteristics. There was no difference in OS between the left and right side localization in any RAS-mutant mCRC patients (22.1 vs. 27.9 months, respectively, p=0.19), whereas patients with all RAS-wild type tumor in the right colon were associated with a worse OS than left-sided counterparts (19.4 vs 29.9 months, respectively, p=0.01). Multivariate analysis revealed that the right-sided tumor (HR, 1.74; 95% CI: 1.165-2.608; p=0.007), the presence of comorbid disease (HR, 1.58; 95% CI: 1.079-2.321, p=0.019), body mass index (BMI) <25 ( HR, 1.61; 95% CI: 1.108-2.352, p=0.013), grade III tumor (HR, 1.65; 95% CI: 1.109-2.457, p=0.014), and being unable to metastasectomy (HR, 2.10; 95% CI: 1.235-3582, p=0.006) were found to be independent predictors of worse survival.


While right side localization was an independent negative predictor of survival in patients with mCRC, tumor sidedness was not found to be associated with response to treatment. The worse OS in right localization may be due to the aggressive nature of right-sided colon tumors which show faster progression, since their response to treatment does not appear to be different.

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