Peritoneal carcinomatosis of unknown primary site in women. A distinctive subset of adenocarcinoma.

Study Objective: To define the clinical features and results of systemic treatment in women with adenocarcinoma of unknown primary site involving predominantly the peritoneal surfaces.
Design: Retrospective analysis of 18 patients treated at a single institution between 1978 and 1984.
Patients: All 18 women had abdominal carcinomatosis and had no primary site identified at laparotomy. Nine patients had limited residual tumor (maximal tumor diameter, 3 cm or less) after initial cytoreductive surgery, and 9 patients had extensive residual disease.
Interventions: In general, patients were treated according to standard guidelines for treatment of advanced ovarian carcinoma. All patients had initial laparotomy with attempted cytoreduction; of these 18 patients, 16 subsequently received cisplatin-based chemotherapy. Patients were restaged either clinically (10 patients) or with second-look surgery (8 patients).
Results: The median survival for all patients was 23 months. Five patients had complete response to chemotherapy, and three patients remain disease-free 41, 59, and 77 months after diagnosis. Patients with limited residual disease had longer median survival than did those with extensive residual disease (31 months compared with 11 months).
Conclusions: Women with adenocarcinoma of unknown primary site involving predominantly the peritoneal surface should be distinguished from other patients with adenocarcinoma of unknown primary site because they have a more indolent disease course, a higher response rate to systemic therapy, and a chance for long-term, disease-free survival after therapy. Although optimal treatment is undefined, we recommend that these patients be treated using the guidelines established for therapy of advanced ovarian carcinoma, including initial surgical cytoreduction followed by cisplatin-based combination chemotherapy.