Effect of Isolated Peritoneal and Nonperitoneal Metastasis and Metastatic Sites on Survival in Patients With Colorectal Cancer


Key Points

  • Overall survival was poorer in patients who colorectal cancer who had isolated peritoneal vs isolated nonperitoneal metastasis but did not differ significantly from that in patients who had peritoneal plus one other metastatic site or at least two nonperitoneal metastatic sites.
  • The shortest overall survival was reported in patients with peritoneal metastasis plus at least two additional metastatic sites.

Overall survival was poorer with isolated peritoneal metastasis in colorectal cancer vs other isolated sites of metastasis in patients receiving first-line systemic therapy but similar to that in patients with peritoneal plus another metastatic site and in patients with at least two nonperitoneal sites. These findings were based on an analysis of individual patient data reported in The Lancet Oncology by Franko et al.

Study Details

The analysis involved data on 10,553 patients from 14 phase III randomized trials of first-line systemic therapy between 1997 and 2008 included in the Analysis and Research in Cancers of the Digestive System (ARCAD) database. Multivariate analysis was adjusted for age, sex, Eastern Cooperative Oncology Group performance status, primary tumor location (colon vs rectum), previous treatment, and baseline body mass index.

Patient Characteristics

Of the 10,553 patients, 9,178 (87%) had nonperitoneal metastatic disease, with 4,385 having 1 site of metastasis and 4,793 having at least 2 sites of metastasis. A total of 194 patients (2%) had isolated peritoneal metastatic disease, and 1,181 patients (11%) had peritoneal metastasis and other organ involvement.

The groups were similar with regard to age, ethnic origin, and use of targeted treatment. Patients with vs without peritoneal metastasis were more likely to be women (41% vs 36%, P = .0003), have colon primary tumors (84% vs 66%, P < .0001), and have a performance status of 2 (10% vs 6%, P < .0001). Among patients with available data, mutated BRAF was more common in patients with peritoneal-only metastasis (18%) and peritoneal and other metastatic sites (12%), compared with nonperitoneal metastasis (9%).

Overall Survival Outcomes

Compared with patients with isolated peritoneal metastasis, overall survival was significantly better in those with isolated nonperitoneal sites (adjusted hazard ratio [HR] = 0.75, P = .003) but similar in those with at least two nonperitoneal sites (adjusted HR = 1.04, P = .69) and in those with peritoneal metastasis plus one other site of metastasis (adjusted HR = 1.10, P = .37). Compared with patients with isolated peritoneal metastasis, patients with peritoneal metastasis plus at least two additional sites of metastasis had the shortest overall survival (adjusted HR = 1.40, P = .0011).

The investigators concluded: “Patients with peritoneal metastatic colorectal cancer have significantly shorter overall survival than those with other isolated sites of metastases. In patients with several sites of metastasis, poor survival is a function of both increased number of metastatic sites and peritoneal involvement. The pattern of metastasis and in particular, peritoneal involvement, results in prognostic heterogeneity of metastatic colorectal cancer.”

Jan Franko, MD, of Mercy Medical Center, Des Moines, is the corresponding author of The Lancet Oncology article.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.