Risk of metachronous peritoneal metastases in patients with pT4a versus pT4b colon cancer: An international multicentre cohort study

Vivian P Bastiaenen, Arend G J Aalbers, Alvaro Arjona-Sánchez, Vittoria Bellato, Jarmila D W van der Bilt, André D D'Hoore, Esther Espinosa-Redondo, Charlotte E L Klaver, Iris D Nagtegaal, Bert van Ramshorst, Hjalmar C van Santvoort, Giuseppe S Sica, Petur Snaebjornsson, Karin A T G M Wasmann, Johannes H W de Wilt, Albert M Wolthuis, Pieter J Tanis

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INTRODUCTION: With evolving treatment strategies aiming at prevention or early detection of metachronous peritoneal metastases (PM), identification of high-risk colon cancer patients becomes increasingly important. This study aimed to evaluate differences between pT4a (peritoneal penetration) and pT4b (invasion of other organs/structures) subcategories regarding risk of PM and other oncological outcomes.

MATERIALS AND METHODS: From eight databases deriving from four countries, patients who underwent curative intent treatment for pT4N0-2M0 primary colon cancer were included. Primary outcome was the 5-year metachronous PM rate assessed by Kaplan-Meier analysis. Independent predictors for metachronous PM were identified by Cox regression analysis. Secondary endpoints included 5-year local and distant recurrence rates, and 5-year disease free and overall survival (DFS, OS).

RESULTS: In total, 665 patients with pT4a and 187 patients with pT4b colon cancer were included. Median follow-up was 38 months (IQR 23-60). Five-year PM rate was 24.7% and 12.2% for pT4a and pT4b categories, respectively (p = 0.005). Independent predictors for metachronous PM were female sex, right-sided colon cancer, peritumoral abscess, pT4a, pN2, R1 resection, signet ring cell histology and postoperative surgical site infections. Five-year local recurrence rate was 14% in both pT4a and pT4b cancer (p = 0.138). Corresponding five-year distant metastases rates were 35% and 28% (p = 0.138). Five-year DFS and OS were 54% vs. 62% (p = 0.095) and 63% vs. 68% (p = 0.148) for pT4a vs. pT4b categories, respectively.

CONCLUSION: Patients with pT4a colon cancer have a higher risk of metachronous PM than pT4b patients. This observation has important implications for early detection and future adjuvant treatment strategies.

Original languageEnglish
Pages (from-to)2405-2413
Number of pages9
JournalEuropean Journal of Surgical Oncology
Issue number9
Publication statusPublished - Sept 2021


  • Locally advanced colon cancer
  • Oncological outcomes
  • Peritoneal metastases
  • Survival
  • T4 colon cancer


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