Radiologically occult metastatic pancreatic cancer: how can we avoid unbeneficial resection?

This study aimed to clarify the key factors for minimizing unsuitable surgical interventions for patients with radiologically occult metastatic pancreatic cancer (ROMPC), defined as a distant metastasis detected during surgery or within 6 months after resection.

This study involved 502 patients planned to undergo curative resection for pancreatic cancer between 2008 and 2015. Patients were divided into ROMPC and non-ROMPC groups and evaluated preoperative factors associated with ROMPC.

Overall survival (OS) was significantly lower in the ROMPC group (n = 145) than the non-ROMPC group (n = 357, median survival time [MST] 10.8 vs. 35.3 months, P < 0.001). In the ROMPC group, OS tended to be worse for patients who had pancreatectomies (n = 84) than those who did not (n = 61, MST 10.1 vs. 13.2 months, P = 0.057), and the next chemotherapy started significantly later in patients who had pancreatectomies (P < 0.001). Moreover, OS was significantly lower for patients with (n = 82) than without (n = 63) liver metastases (MST 9.7 vs. 13.0 months, respectively, P = 0.020). The best indicator for patients at higher risk of ROMPC was a combination of carbohydrate antigen 19-9 concentration ≥ 300 U/ml and tumor size ≥ 30 mm.

In the ROMPC group, patients who underwent pancreatectomy had a poorer prognosis than patients not undergoing pancreatectomy. Given that the liver was the most frequent distant metastatic site for ROMPC and had the poorest prognosis, establishing a strategy featuring new imaging modalities to detect radiologically occult liver metastases is necessary.