Synchronous peritoneal metastases of small bowel adenocarcinoma: Insights into an underexposed clinical phenomenon.

BACKGROUND: The aim of this population-based study was to provide insight into the incidence, risk factors and treatment-related survival of patients with peritoneal metastases (PM) of small bowel adenocarcinoma (SBA).

METHODS: Data from the Netherlands Cancer Registry were used. All patients diagnosed with SBA between 2005 and 2014 were included. The influence of patient and tumour characteristics on the odds of developing PM was analysed. Subsequently, for all further analyses, patients without synchronous PM of SBA were excluded. The log-rank test and Kaplan-Meier analyses were conducted to estimate survival, and the Cox proportional hazards model was used to evaluate the risk of death.

RESULTS: Of the 1428 included patients diagnosed with SBA, 181 (13%) presented with synchronous PM. Synchronous PM was found in 9% of the duodenal tumours and in 17% of the more distal tumours. Median overall survival of all patients with PM was 5.9 months, whereas survival of both 11 months was observed in patients treated with primary tumour resection or palliative chemotherapy and 32 months after cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (CRS+HIPEC). Poor prognostic factors for survival were age ≥70 years (hazard ratio [HR] 1.6, 95% confidence interval [CI] 1.1-2.2), systemic metastases other than PM (HR 2.0, 95% CI 1.4-2.9) and an advanced (HR 1.9, 95% CI 1.3-3.0) or unknown T-stage (HR 2.1, 95% CI 1.2-3.5).

CONCLUSIONS: Synchronous PM was frequently encountered in SBA. Without treatment, prognosis was extremely poor. Survival was higher after primary tumour resection, palliative chemotherapy and CRS+HIPEC, but selection bias probably played a significant role calling for further clinical research.