Peritoneal carcinomatosis from an unknown primary site. Management of 15 patients.

AIMS AND BACKGROUND: Peritoneal carcinomatosis from an unknown primary site is a rare and ill-defined entity. This work attempts to identify clinical and pathological features of patients with this disease and report the results of an aggressive combined treatment modality.

METHODS: Retrospective analysis was performed of medical records of 15 patients with peritoneal carcinomatosis with no primary site identified at a single institution between 1989 and 2000. A primary gastrointestinal cancer was ruled out after a thorough endoscopic and radiologic work-up and complete exploratory surgery.

RESULTS: Four women and 11 men were identified; the average age was 49 years. All patients had cytoreductive surgery with peritonectomies; 4 patients underwent a second-look operation. Perioperative intraperitoneal chemotherapy was given to 10 of the 15 patients, and 9 patients received post-cytoreduction chemotherapy given intraperitoneally (1), systemically (7) or both intraperitoneally and systemically (1). Overall median survival from diagnosis was 19.0 months; 1 patient is alive with disease at 21 months; and 3 patients are disease-free at 17, 38, and 60 months from diagnosis. Significant positive predictive factors for survival were a small volume of ascites (P = 0.02), a large number of peritonectomies performed (P = 0.001), second-look cytoreduction (P = 0.003), perioperative intraperitoneal chemotherapy (P = 0.008) and postoperative chemotherapy (P= 0.01), either intraperitoneal or systemic.

CONCLUSIONS: Peritoneal carcinomatosis from an unknown primary site is a rare subset of primary peritoneal malignancy. Aggressive treatment may provide prolonged palliation with occasional long-term survival.