A real-world analysis of metastasectomy in patients with small intestinal adenocarcinoma presenting with metastasized disease

Background: Small intestinal adenocarcinoma (SIA) is a rare gastrointestinal malignancy, often diagnosed at an advanced stage, resulting in poor overall survival (OS). Limited disease specific treatment guidelines are available, especially regarding patients with metastatic disease. This study aims to describe observed differences in OS according to surgical and systemic treatment options in Dutch patients with SIA with metastases at the time of diagnosis. Methods: This nationwide observational cohort study included all patients diagnosed with synchronous metastatic SIA in the Netherlands between 2009 and 2022, based on data from the Netherlands Cancer Registry. Metastatic patterns, treatment, overall survival and multivariable Cox regression analyses were reported. Results: A total of 983 patients with synchronous metastatic SIA were included. In total, 402 patients (41%) were identified with liver-only metastases, 227 patients (23%) with peritoneum-only metastases and 354 patients (36%) had multiple-site metastases. Metastasectomy was performed in 28 patients with liver-only metastases (7%) and 26 patients with peritoneum-only metastases (12%). Patients who underwent a metastasectomy (including HIPEC for patients with peritoneal metastases) showed a longer observed mOS compared to those with best supportive care or systemic treatment, with or without primary tumor resection, both in patients with liver-only metastases (mOS 34.9mo [20.3-51.9] vs 3.3mo [2.9-4.0], p < 0.001) and patients with peritoneum-only metastases (mOS 21.1mo [14.0-29.2] vs 6.3mo [4.9-7.7], p < 0.001). In multivariable analyses, metastasectomy was associated with longer OS for both subgroups. Conclusion: Although metastasectomy is rarely performed in patients with metastatic SIA, these population-based data show that carefully selected patients with single-site involvement had longer observed survival following metastasectomy.