A retrospective study of risk and prognostic factors in relation to lower respiratory tract infection in elderly lung cancer patients.

Lung cancer (LCa) is one of the most common and deadly malignancies in elderly patients. During the course of the disease, these patients frequently present with lower respiratory tract infection. Therefore, this study aims to investigate the clinical features of lower respiratory tract infection in elderly LCa patients and evaluate the impact on overall survival rate. Clinical and laboratory data were analyzed retrospectively for a total of 1936 patients that were over 60-years-old. Patients were classified into three groups based on pulmonary diseases: Group 1, lung cancer (LCa); Group 2, chronic obstructive pulmonary disease (COPD); and Group 3, other medical diseases without pulmonary problems (OMD). Univariate and multivariate analysis were used to evaluate related risk factors of infections and prognostic factors. The infection rate of the LCa group (46.25%) was significantly higher than the COPD (31.40%) and OMD (23.33%) groups. Polymicrobial infections were most prevalent in the LCa group (28.75%), which far exceeded the prevalence in COPD (11.05%) and OMD (4.44%) groups. In LCa patients, the most frequent pathogens were Gram-negative bacteria (44.87%), followed by fungi (34.62%) and Gram-positive bacteria (20.51%), the major pattern of polymicrobial infections was mixed Gram-negative bacteria and fungi (43.48%). Multivariate analysis revealed that COPD, pleural effusion, anatomical type, low cellular immune function, and length of hospital stay were related risk factors of lower respiratory tract infection in elderly LCa patients. A multivariate Cox proportional hazards regression model revealed that age, stage of TNM, surgical resection, antitumor therapy, lower respiratory tract infection, COPD, and pleural effusion were independent prognostic factors for cancer-related death. Patients who received effective antimicrobial treatment had a better outcome than those who did not respond to antimicrobial drugs (HR = 0.458, P < 0.05). Understanding lower respiratory tract infection in elderly LCa patients is vital if we are to set up corresponding measures and to target effective antimicrobial treatment.