The effect of radiation-induced xerostomia on saliva and serum lysozyme and immunoglobulin levels.

Saliva and serum lysozyme, immunoglobulin, albumin, and total protein levels were monitored in thirty patients with cancer of the head or neck before, during, and after radiotherapy and compared with those of a group of non-irradiated noncancer control subjects. The mean volume-based saliva lysozyme and total protein concentrations were significantly higher in the cancer patients before radiotherapy than in the control group. During radiotherapy, the mean volume-based concentrations of all protein components assayed increased as the saliva flow rate decreased. Protein-based ratios of saliva albumin, IgG, and lysozyme and the ratio of IgG/IgA increased as the xerostomia intensified. Ratios of saliva total protein and IgA to flow rate paralleled the flow rate decrease. Such increased concentrations in saliva immunoproteins were offset, however, by a greater than 93 per cent reduction in total saliva output. This reduced saliva output, therefore, resulted in an immunoprotein deficit. There were no significant differences between the mean serum lysozyme levels of the cancer and control groups at any point of comparison. The mean serum immunoglobulin concentrations in the cancer patients before radiotherapy were significantly higher than those in the control group. During radiotherapy, there was a decrease in the mean serum total protein, albumin, and immunoglobulin levels which reverted toward the pretreatment values during the postirradiation period.