Rheumatoid factor and tumor-host interaction.

In this survey for rheumatoid factor (RF) seropositivity on patients with neoplasms, an 85% rate of positive screening tests was recorded under certain circumstances. This high rate of RF seropositivity occurred after irradiation and/or chemotherapy of breast and lung cancers. Treated patients with breast cancers who had no evidence of residual tumor had an 89% rate of positive RF tests. Conversely, the incidence of RF seropositivity was low among untreated patients with similar tumors and treated patients with glioblastomas or multiple myeloma. The administration of cytotoxic drugs (e.g., azathiprene) was not itself associated with RF production even in renal allograft recipients. The data indicate that RF production occurs frequently after therapy of certain tumors and suggest that in these circumstances RF may be an expression of tumor-host interaction.