Unfavorable cancers of unknown primaries: presentation and prognostic factors. A population-based 8-year experience.

Cancer of unknown primary is a mostly disseminated malignancy where detailed investigations cannot reveal a probable origin. A few subsets may respond to specific therapy, but the large majority of cases have a median survival of 3-4 months in the few population-based reports, which, however, did not use current investigations and therapy. It is not known if survival can be prolonged by chemotherapy or if supportive care is preferable, especially in the most unfavorable cases in whom chemotherapy may impair the quality of life without prolonging it. We therefore studied prognosis of 134 recent population-based consecutive unfavorable patients. Multiple involvements of the liver, nodes, lungs and skeleton, polysymptomatology, and biochemical abnormalities were common. The median survival time was 103 days, and the 1-year survival was 19%. Hypoalbuminemia, weight loss, and anemia in this order were the strongest negative prognostic factors in multivariate analysis, but univariate analysis added involvement of multiple sites or of the liver, high age, male gender, adenocarcinoma histology, and tobacco use as unfavorable factors. About 10% of patients became long-term survivors, sometimes in the presence of one or more of negative prognostic factors but in particular those with limited nodal spread. A previously unreported finding was that nodal involvement of squamous cell carcinoma limited to the iliacoinguinal region could seemingly be cured by surgery ± radiotherapy. In the absence of efficient treatment and controlled therapeutic trials, supportive care alone seems justified for patients with the worst prognostic factors.