Background: The etiology and distribution of community-acquired pneumonia (CAP) vary periodically and geographically. The clinical evaluation of CAP among patients with cancers remains unknown.
Patients and Methods: This retrospective hospital-based study on adult CAP was conducted in Tang Du Hospital, China, from September 2018 to August 2019. The demographic characteristics, clinical manifestations and laboratory data were extracted from medical records and compared between CAP patients with and without cancers. Univariable and multivariable logistic regression methods were used to explore risk factors associated with CAP patients with and without cancers.
Results: Data from 149 CAP patients with cancers and 268 CAP patients without cancers were analyzed. Patients without cancers were more likely to show fever, cough and yellow sputum, higher level of neutrophil count than the cancer patients. Klebsiella pneumoniae  (K. pneumoniae  14.77% vs 9.33%, p = 0.093) and Streptococcus pneumoniae  (S. pneumoniae  16.11% vs 11.57%, p = 0.189) were among the most commonly encountered pathogens in both the groups. Pseudomonas aeruginosa  (P. pneumoniae  26.50% vs 11.41%, p < 0.001), Mycoplasma pneumoniae  (M. pneumoniae  8.21% vs 1.34%, p = 0.003), and filamentous fungi (10.82% vs 4.7%, p = 0.033) were predominant in CAP patients without cancers. Haemophilus influenzae  (H. influenzae  22.15% vs 14.18%, p = 0.038) and methicillin-resistant Staphylococci  (MRS 23.49 vs 15.68, p = 0.049) were more prevalent for CAP cancer patients. Certain pathogens were increasing in a cold season. In patients without cancers, MRS, H. influenzae  and P. aeruginosa  were associated with central nervous system (CNS) disease, connective tissue disease, bronchiectasis, respectively. In addition, healthy adults were likely to be infected with M. pneumoniae  showing fever.
Conclusion: CAP patients with cancers had atypical clinical manifestations and showed no distinct increase in inflammatory markers. The predominant pathogens differed as well as similar between the CAP patients with and without cancers. Certain pathogens follow a seasonal pattern. CNS disease, connective tissue disease and bronchiectasis were associated with the predominant pathogens in patients without cancers.
Keywords: community-acquired pneumonia, etiology, pathogen, epidemiology, cancer