Abstract
Background: So far, optimization problems for diagnostics and prognostication aids have been still relevant for lung cancer as a leader in the structure of cancers.

Aims and Objectives: A search for regularities of changes in the saliva enzyme activity in patients with lung cancer.

Materials and Methods: In the case-control study, 859 people divided into two groups took part: Primary (lung cancer, n = 286) and control (conventionally healthy, n = 573). All the participants went through a questionnaire survey, saliva biochemical counts, and a histological verification of their diagnosis. The enzyme activity was measured by spectrophotometry. Between group differences were measured with the nonparametric test.

Results: In terms of lung cancer, we observe metabolic changes described with decreased de Ritis coefficient (P ˂ 0.001), as well as the increased activity of alanine aminotransferase (P = 0.022), alkaline phosphatase (P ˂ 0.001), gamma-glutamyl transpeptidase (P = 0.043), and α-amylase (P ˂ 0.001). We have identified specifics of the change in the enzyme activity depending on a histological type and a growth form of the tumor. There is the observable increased activity of α-amylase in the saliva in lung adenocarcinoma and neuroendocrine tumors (P ˂ 0.001). It has been found that irrespective of the histological type of lung cancer in a transition from central to peripheral forms of growth; there is the observable increased activity of all the enzymes. The significantly reduced activity of aspartate aminotransferase (by 51.4% for adenocarcinoma, P = 0.032; 48.8% for squamous cell lung cancer, P = 0.042) is a distinctive feature of central lung cancer.

Conclusion: The nature of the change in the enzyme activity is ambiguous and to a greater degree depends on the tumor form of growth (central/peripheral lung cancer) than the histological type (adenocarcinoma/squamous cell lung cancer).

Key words: Saliva; Aminotransferase; Lactate Dehydrogenase; Gamma-glutamyl Transpeptidase; Alkaline Phosphatase; α-Amylase