Introduction: – To investigate the incidence of, factors associated with, and differences between synchronous and metachronous colorectal peritoneal metastases (CPM) in a population-based cohort. Methods: – Data from the Netherlands Cancer Registry were used. All patients diagnosed with colorectal cancer (CRC) between 1 January and June 30, 2015 were evaluated for synchronous or metachronous CPM (diagnosis ≤90 or >90 days after surgery for primary CRC), and survival in 2019 (median follow-up 38.4 months). Results: – Of 7233 included patients, 409 (5.7%) were diagnosed with synchronous CPM. Factors associated with synchronous CPM were mucinous (OR 2.72 [1.90–3.90]) or signet ring cell (SRC) histology (OR 6.58 [3.66–11.81]), T4 (OR 4.82 [3.68–6.32]), N1 (OR 1.66 [1.20–2.30]), or N2 stage (OR 3.27 [2.36–4.52]), and synchronous systemic metastases (SM) (OR 3.13 [2.37–4.14]). After surgery for primary CRC, 326 patients developed metachronous CPM after a median time of 14.7 months (3-year cumulative incidence: 5.5%). Factors associated with metachronous CPM were younger age (HR 1.63 [1.10–2.42]), mucinous (HR 1.84 [1.20–2.82]) or SRC histology (HR 2.43 [1.11–5.32]), T4 (HR 2.77 [2.07–3.70]), N1 (HR 2.90 [2.18–3.85]), N2 (HR 3.19 [2.26–4.50]), and synchronous SM (HR 1.95 [1.43–2.66]). Conclusion: – This population-based study found the highest incidence of CPM currently reported in literature and a strong association between the presence of synchronous SM and both synchronous and metachronous CPM. These findings may contribute to a tailored approach in the follow-up after primary CRC surgery and guide future clinical trials investigating new strategies regarding risk-reduction or early detection of metachronous CPM.

Colorectal cancer, Incidence, Peritoneal metastases, Risk factors,
European Journal of Surgical Oncology
No Subscription.
Department of Surgery

Lurvink, R.J. (R. J.), Bakkers, C. (C.), Rijken, A.M, van Erning, F.N, Nienhuijs, S.W, Burger, J.W.A, … de Hingh, I.H.J.T. (2020). Increase in the incidence of synchronous and metachronous peritoneal metastases in patients with colorectal cancer: A nationwide study: Colorectal PM: incidence & associated factors. European Journal of Surgical Oncology. doi:10.1016/j.ejso.2020.11.135