The Significance of Sidedness in Patients with Metastatic Colorectal Cancer Treated with Triplet First-line Chemotherapy

Background: Recent data have shown that right-sided colon cancer carries poorer prognosis compared to left-sided tumors. This study was aimed to evaluate the progression-free survival, overall survival of patients with metastatic colon cancer of right-sided versus left-sided primaries treated with triplet chemotherapy regimen. Methods: The medical records of patients with metastatic colorectal cancer treated on phase I-II trial of combination Irinotecan, oxaliplatin, capecitabine, and bevacizumab were reviewed for sidedness of the primary. The analysis was performed for progression-free survival and overall survival according to the sidedness and other known prognostic factors. Results: Out of 53 patients treated with triplet therapy, 11 had right sided and 42 had left-sided primaries. The median age for right-sided primaries was 46 (range 24-55) compared to 53 (range 32-74) in left-sided primaries. Median progression-free survival was 14 months for right vs 18 months for left sided tumors (Hazard ratio 0.72, 95% confidence interval 0.27-1.88, p=0.492) and median overall survival was 21 months for right vs 29 months for left sided tumors (Hazard ratio was 0.86, 95% CI 0.32-2.26, p=0.752). Conclusion: First-line triplet chemotherapy may overcome the difference in prognosis between right sided and left sided primaries in metastatic colorectal cancer. A larger analysis is warranted.