Importance: Little is known about the risk of post-COVID-19 multisystem inflammatory syndrome in children (MIS-C) in the setting of childhood cancer.
Objective: To evaluate factors associated with MIS-C and describe the clinical course of COVID-19 in the setting of MIS-C.
Design, setting, and participants: Multisite observational cohort study of a registry representing more than 100 US pediatric oncology sites. All included patients were registered between April 1, 2020, and May 18, 2022. Sites submitted deidentified data surrounding sociodemographics, cancer diagnosis and treatment, and COVID-19 course (symptoms, maximum support required, outcome). Patients with MIS-C (n = 24) were compared with matched controls (n = 96). Children (<21 years) with cancer who developed COVID-19 while receiving cancer treatment or within 1 year of completing treatment were characterized based on their development of MIS-C.
Exposures: (1) Clinical and sociodemographic characteristics of children with cancer and COVID-19; and (2) MIS-C.
Main outcomes and measures: (1) Development of MIS-C among children with cancer and COVID-19; and (2) symptoms and disease severity associated with MIS-C.
Results: Among 2035 children with cancer and COVID-19, 24 (1.2%) developed MIS-C. COVID-19 occurred at a median (IQR) age of 12.5 (5.5-17.1) years in those with MIS-C and 11 (6-16) years among matched controls (P = .86). The majority of children with MIS-C had a hematologic cancer (83.3% [n = 20]), were publicly insured (66.7% [n = 16]), and were Hispanic (54.2% [n = 13]). Half (n = 12) had 1 or more noncancer comorbidity. Those with comorbidities were more likely to develop MIS-C than those without (odds ratio [OR], 2.5 [95% CI, 1.1-5.7]). Among children with MIS-C, 100% (n = 24) were admitted to the hospital and 54.2% (n = 13) to the intensive care unit (ICU), while COVID-19 contributed to the death of 20.1% (n = 5); cancer therapy was changed in 62.5% (n = 15). Compared with matched controls, those with MIS-C had higher odds of symptoms classified as systemic (OR, 4.7 [95% CI, 1.4-15.8]) or gastrointestinal (OR, 5.0 [95% CI, 1.7-14.6]) along with higher odds of hospitalization (OR, 42.9 [95% CI, 7.1-258]), ICU admission (OR, 11.4 [95% CI, 3.6-36.4]), and changes to cancer therapy (OR, 24.9 [95% CI, 6.5-94.8]).
Conclusions and relevance: In this cohort study among children with cancer and COVID-19, those with MIS-C had a more severe clinical course than those without MIS-C. The risk of MIS-C and its severity are important to consider as clinicians monitor patients with COVID-19. These findings can inform their conversations with families regarding COVID-19 risks and the benefits of prevention strategies that are pharmacologic (vaccination) and nonpharmacologic (masking), as well as treatment (antivirals, monoclonal antibodies).