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 resu lts of an aggressive combined treatment modality. Methods: Retrospective analysis was performed of medical records of 15 pati ents with peritoneal carcinomatosis with no primary site identified at a si ngle institution between 1989 and 2000. A primary gastrointestinal cancer w as ruled out after a thorough endoscopic and radiologic work-up and complet e exploratory surgery. Results: Four women and 11 men were identified; the average age was 49 year s. All patients had cytoreductive surgery with peritonectomies; 4 patients underwent a second-look operation. Perioperative intraperitoneal chemothera py was given to 10 of the 15 patients, and 9 patients received post-cytored uction chemotherapy given intraperitoneally (1), systemically (7) or both i ntraperitoneally and systemically (1). Overall median survival from diagnos is was 19.0 months; 1 patient is alive with disease at 21 months; and 3 pat ients 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-l ook cytoreduction (P = 0.003), perioperative intraperitoneal chemotherapy ( P = 0.008) and postoperative chemotherapy (P = 0.01), either intraperitonea l or systemic. Conclusions: Peritoneal carcinomatosis from an unknown primary site is a ra re subset of primary peritoneal malignancy. Aggressive treatment may provid e prolonged palliation with occasional long-term survival.