Epidemiology of carcinomatosis

Carcinomatosis is an advanced form of metastatic cancer, which has been thought to be an invariantly fatal disease. We characterized prognostic factors for overall survival (OS) in patients with de-novo carcinomatosis.

Patients were identified from the SEER database from 1/1/2016-12/31/2020. Kaplan-Meier method and log-rank test were used to evaluate OS and a Cox proportional hazards model was used to calculate adjusted hazard ratios (aHR) with 95 % confidence intervals (CIs). We included patients with carcinomatosis across 30 primary sites. The most common primary tumors were colorectal, pancreas, ovary, and lung & bronchus, and stomach.

Among newly diagnosed cancer patients in SEER, a total of 3131 (59.7 % female, 80.1 % White) patients with carcinomatosis were identified, corresponding to an incidence of 9.0 per 1000,000 persons. Of all patients with metastatic disease, only 0.17 % were diagnosed with carcinomatosis. Compared to patients with de novo metastatic disease without carcinomatosis (i.e., those with metastases limited to the brain, bone, liver, or lung), patients with carcinomatosis were associated with over twice the risk of mortality (aHR = 2.3, 95 % CI: 2.2-2.5). The 1-year OS for patients with carcinomatosis was 35.8 % (95 % CI: 34.0 %-37.7 %). The most common primary sites included: colorectal (14.8 %), pancreas (14.8 %), ovary (9.8 %), and lung & bronchus (8.9 %). Patients with appendiceal (1-year OS: 88.2 %, 95 % CI: 81.8 %-95.1 %) and ovarian (1-year OS: 58.7 %, 95 % CI: 53.0 %-65.0 %) carcinomatosis had markedly longer survival compared to patients with carcinomatosis from other primary sites. Patients who were at highest risk of death are more likely to be older; male; Black; have more advanced T and N categories; and/or have synchronous metastases (P < .001).

Carcinomatosis is associated with poorer OS compared to other forms of metastases. Patients with ovarian and appendiceal tumors have markedly longer survival.