A systematic review and meta-analysis of the incidence of Pneumocystis jirovecii pneumonia (PJP) in children and young people with cancer, cancer-like conditions or haematopoietic stem cell transplants

Pneumocystis jirovecii Pneumonia (PJP) is a potentially life-threatening fungal infection occurring in immunocompromised individuals, particularly those receiving anti-cancer treatment. However, the incidence of PJP among children and young people (CYP) with cancer, cancer-like conditions or haematopoietic stem cell transplant (HSCT) recipients is unclear. This systematic review aimed to determine the incidence and impact of PJP in this population. Twelve databases were searched in November 2024. Any study reporting the incidence of PJP in CYP<18 years old with cancer, a cancer-like condition or having received a HSCT were included. Screening, data extraction and quality assessment (using a modified JBI critical appraisal tool for prevalence studies) were conducted in duplicate. Meta-analyses using GLMM methods were used. Of 7,194 records screened, 106 studies were included. Interpretation of the results of many studies was hindered by limited reporting. For the acute lymphoblastic leukaemia meta-analyses using confirmed events, higher pooled cumulative incidence rates were seen in the no prophylaxis group than in the prophylaxis group (2.86% vs 0.04%). Rates increased to 5.41% in the no prophylaxis group when studies reporting unconfirmed cases were included. Subgroup analyses suggested lower incidence rates in cohorts taking first-line PJP prophylaxis, compared to second-line. The cumulative incidence rate using confirmed events was 0.16% for HSCT patients receiving prophylaxis; data were not available for a no prophylaxis analysis. Only three studies were available for the HSCT total events analysis, producing a rate of 4.27%. Several analyses were subject to some uncertainty due to their high heterogeneity estimates. PROSPERO registration: CRD42025628682