Carcinoma of unknown primary: natural history and response to therapy.

Twenty-three consecutive patients with metastatic carcinoma of unknown primary referred to a medical oncology service over the past two years were studied. In the majority of patients, death occurred within one year of diagnosis and a priamry site of disease was identified at postmortem examination. Of patients who had a primary site identified, findings suggestive of involvement of that site were present during the course of their illness. Survival was greatest in patients with adenocarcinoma histology, with lymph node site of presentation and in those treated with both radiation therapy and chemotherapy, although these differences were not statistically significant. Despite the prolonged survival of a few patients, it is clear that failure to extensively evaluate subtle clinical findings and the lack of efficacious therapy for the malignancies commonly encountered seriously limit the survival of the vast majority of these patients. The identification of new tumor markers and the use of adjunctive chemo-immunotherapy to excisional surgery may ultimately improve to outlook for these patients.