Prognostic significance of peritoneal metastasis from colorectal cancer treated with first-line triplet chemotherapy

Background: Peritoneal metastasis from colorectal cancer (CRC) carries a poor prognosis in most studies. The majority of those studies used either a single-agent or doublet chemotherapy regimen in the first-line setting.

Aim: To investigate the prognostic significance of peritoneal metastasis in a cohort of patients treated with triplet chemotherapy in the first-line setting.

Methods: We retrospectively evaluated progression-free survival (PFS) and overall survival (OS) in 51 patients with metastatic CRC treated in a prospective clinical trial with capecitabine, oxaliplatin, irinotecan, and bevacizumab in the first-line setting according to the presence and absence of peritoneal metastasis. Furthermore, univariate and multivariate analyses for PFS and OS were performed to assess the prognostic significance of peritoneal metastasis at the multivariate level.

Results: Fifty-one patients were treated with the above triplet therapy. Fifteen had peritoneal metastasis. The patient characteristics of both groups showed a significant difference in the sidedness of the primary tumor (left-sided primary tumor in 60% of the peritoneal group vs 86% in the nonperitoneal group, P = 0.03) and the presence of liver metastasis (40% for the peritoneal group vs 75% for the nonperitoneal group, P = 0.01). Univariate analysis for PFS showed a statistically significant difference for age less than 65 years (P = 0.034), presence of liver metastasis (P = 0.046), lung metastasis (P = 0.011), and those who underwent metastasectomy (P = 0.001). Only liver metastasis and metastasectomy were statistically significant for OS, with P values of 0.001 and 0.002, respectively. Multivariate analysis showed that age (less than 65 years) and metastasectomy were statistically significant for PFS, with P values of 0.002 and 0.001, respectively. On the other hand, the absence of liver metastasis and metastasectomy were statistically significant for OS, with P values of 0.003 and 0.005, respectively.

Conclusion: Peritoneal metastasis in patients with metastatic CRC treated with first-line triple chemotherapy does not carry prognostic significance at univariate and multivariate levels. Confirmatory larger studies are warranted.