Incidence and Risk Factors of Community-Acquired Pneumonia in Hematologic Oncologic Patients

Introduction

Patients with hematologic malignancies are immunocompromised due to the underlying disease and the administration of immunosuppressive antineoplastic therapy. Community-acquired pneumonia is a common and serious infectious complication in these patients, accompanied by significant morbidity, mortality, and increased treatment costs. According to studies, the most frequently isolated agent is Streptococcus pneumoniae, responsible for approximately 20% of cases. Pneumococcal infection also often precedes severe invasive pneumococcal disease.

The last study assessing the incidence of community-acquired pneumonia was conducted between 2011 and 2015. Until now, newer epidemiological data were missing, and the insights into potential risk factors for community-acquired pneumonia in this patient group were very limited. In recent years, there has also been further progress in immunomodulatory therapy options, including biological treatment with anti-CD20 antibodies, which may have further altered the risk of infectious complications in hematologic oncologic patients.

Thus, a cohort non-interventional study with a control analysis conducted by Dutch authors brings new information about the epidemiology of community-acquired pneumonia and simultaneously identifies risk factors for the disease in hematologic oncologic patients during the period of 2016-2019.

Study Methodology

Adult patients with hematologic malignancies from two large tertiary hospitals in Amsterdam were included in the cohort study from January 1, 2016, to December 31, 2019. The primary goal of the study was to determine the incidence rate (IR) of community-acquired pneumonia in hematologic oncologic patients stratified by disease subtype. Secondary goals included identifying the causative microbiological agents and risk factors associated with community-acquired pneumonia and evaluating severe cases of the disease defined by death associated with community-acquired pneumonia within 30 days and/or intensive care unit admission due to community-acquired pneumonia. For this purpose, a control analysis was performed, with controls matched to patients in a 1:1 ratio based on hematologic malignancy subtype.

Findings

During the observation period, a total of 275 cases of community-acquired pneumonia were observed during 6246 patient-years of the observation period. The incidence rate of community-acquired pneumonia was thus 4390/100,000 patient-years compared to the incidence of 275/100,000 patient-years in the general hospital population. The risk of community-acquired pneumonia was increased in all subtypes of hematologic malignancies with IR ranging from 5.4 to 55.3 depending on malignancy subtype and treatment status.

The highest incidence rate was observed in patients after autologous or allogeneic hematopoietic stem cell transplantation, as well as in patients with acute myeloid leukemia, acute lymphoblastic leukemia, or multiple myeloma. The most frequently identified pathogen was Streptococcus pneumoniae (24 cases), followed by rhinoviruses, parainfluenza viruses, and Haemophilus influenzae bacteria.

The hospitalization rate, need for intensive care admission, and mortality due to community-acquired pneumonia were 67.4%, 9.8%, and 5.5%, respectively. The highest hospitalization and intensive care unit admission rates were observed in cases of pneumococcal pneumonia. Statistically significant predictors of community-acquired pneumonia in the final multivariate analysis included male gender, anemia, lymphocytopenia, cardiovascular disease, chronic kidney disease, history of autologous or allogeneic hematopoietic stem cell transplantation, immunosuppressive medication in the context of graft versus host disease (GvHD), anti-CD20 antibody rituximab treatment within 1 year before the onset of community-acquired pneumonia, and treatment with immunomodulators (lenalidomide, thalidomide, pomalidomide, and/or methotrexate) within 1 month before the onset of community-acquired pneumonia.

Independent predictive factors for severe disease course identified in the multivariate analysis included neutropenia (odds ratio [OR] 4.14; 95% confidence interval [CI] 1.63–10.2), pneumococcal pneumonia (OR 10.24; 95% CI 3.48–30.1), chronic obstructive pulmonary disease (OR 6.90; 95% CI 2.07–23.0), and the use of antibacterial prophylaxis (OR 2.53; 95% CI 1.05–6.08).

Conclusion

The results of the cited study showed that the incidence rate of community-acquired pneumonia is high in hematologic oncologic patients and that this infection is accompanied by high morbidity and mortality. The authors of the study recommend preventive vaccination against respiratory pathogens in the early stages of the disease, especially before the initiation of certain types of immunosuppressive therapy.

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Source: Certan M., Garcia Garrido H. M., Wong G. et al. Incidence and predictors of community-acquired pneumonia in patients with hematological cancers between 2016 and 2019. Clin Infect Dis 2022 Feb 23; ciac005, doi: 10.1093/cid/ciac005 [Epub ahead of print].