Serologic determinants of survival in patients with squamous cell carcinoma of the head and neck. Specific circulating serum proteins may reflect unique properties governing the growth and progression of head and neck cancers. One hundred three previously untreated patients with squamous cell carcinoma of the head and neck were prospectively evaluated for serum IgA, IgG, and IgM and C1q-binding macromolecules. Immunoglobulins were assessed by the immunoturbidimetric technique. C1q-binding macromolecules (C1qBM) were measured utilizing the iodine-125 assay of Zubler et al (J Immunol 1976; 116: 232-5). Neither the level of serum immunoglobulins nor C1qBM values were correlated with the primary site, AJC (American Joint Committee on Cancer) stage of disease, or size of primary lesion. Likewise, comparison of serum IgA with C1qBM values demonstrated that these laboratory parameters were independent variables (r = 0.15 by Pearson linear regression). Univariate statistical analysis, utilizing the Cox proportional hazard model, showed serum IgA and C1qBM values to each contribute significantly to the ability to predict survival in patients with advanced squamous cell carcinoma of the head and neck (p = 0.01 and 0.003, respectively). Furthermore, multivariate analysis reveals that both C1qBM and serum IgA levels contribute significantly to the hazards model beyond staging in predicting survival (p less than 0.001). Predictive results were most apparent in patients with stage IV disease and related to the probability of both regional and distant metastatic recurrences. Conversely, serologic analysis provided no information in patients who were staged early. These results support pretreatment multiparametric serologic analysis of patients with squamous cell carcinoma of the head and neck. 