The effect of primary tumor localisation on survival and treatment response in metastatic colorectal cancer patients: Retrospective analysis

ABSTRACT Introduction: Colorectal carcinomas are the third most common cancer in the men and the second most common cancer in women. It is responsible for 8% of cancer related deaths in worldwide. The most important prognostic factor is the stage of the disease at the time of diagnosis. 20% of colorectal cancers is metastatic at the time of diagnosis. CALBG/SWOG 80405 and FIRE-3 phase 3 studies are revealed that primary tumour localisation is a prognostic factor for progression-free-survival and overall survival. In this study we aimed to determine prognostic and predictive effect of primary tumour localisation in metastatic colorectal cancer patients whom admitted to medical oncology department of our hospital. Material and Methods:Patients who admitted to Ege University Medical Oncology department between 2010-2015 and diagnosed and treated as metastatic colorectal cancer, included in the study. 1600 patient file was searched, 488 patient data were saved and analyzed. Results: 38,9 % of patients were women and 61,1 % of patients were men. Mean age was 59,8. According to primary tumour localization 86,5 % of patients had left colorectal cancer, 13,5% of patients had right colon cancer.34,6% of patients were found our K-Ras wild type and 26,2% was k-ras mutant. 54,7 % of patients treated with bevacizumab, 5,3% treated with cetuximab and 2,2% treated with panitumumab. Mean progression- free survival was 12,79 months and overall survival was 33,39 months. There was no difference on age and gender according to primary tumour localisation. When compared with targeted therapies, 60.6% of patients with right colon tumor were treated with anti-EGFR antibody and 6.0% (4 patients) of anti-VEGF antibody. In patients with left colon tumors, the proportion of patients receiving anti-VEGF antibody therapy was 53.9% and the rate of patients receiving anti-EGFR antibody was 7.9%. Progression-free survival times were calculated as 12.9 months in the right colon tumor group and 12.7 months in the left colon tumor group (p> 0.05). The mean overall survival time was 31.6 months in the right colon tumor group and 33.6 months in the left colon tumor group (p> 0.05). in KRAS wild type patient arm in left colon cancer patients targeted therapies were compared to each other; in the group receiving anti-VEGF antibody treatment, the mean progression-free survival was 16.4 months and 11.5 months in the anti-EGFR antibody therapy group (p <0.05). When the overall survival time was examined, in patients receiving anti-VEGF antibody treatment the overall survival was 46.2 months and in patients receiving anti-EGFR antibody treatment was 42.3 months (p> 0,05). Progression-free survival and overall survival were not studied because insufficient the number of patients receiving targeted therapy in the K-Ras wild type right colon tumor group. Conclusion: Although we reached out similar progression-free survival and overall survival time with the literature, because of the large patient number difference between two groups, results are not meaningful statistically. Keywords: metastatic colorectal carcinoma, right colon cancer, left colorectal cancer, primary tumour localization, first-line targeted therapy, progression free survival overall survival