Variables
The following variables were considered in the analysis: sex, age at COVID-19 diagnosis, clinical manifestations, type of tumor according to the International Classification of Childhood Cancer - third edition (ICCC-3), requirement for intensive care, specific treatment for COVID-19, and status.
Tumors was coded according to the International Classification of Diseases for Oncology - third edition (ICD-O-3) and the ICCC-3.
Disease severity was defined according to the internationally used clinical classification into 5 degrees of severity: 1) Asymptomatic: no symptoms but a positive COVID-19 test, 2) Mild: outpatient management, gastrointestinal symptoms, upper respiratory tract infection, 3) Moderate: lower respiratory tract involvement, e.g. pneumonia, 4) Severe: oxygen requirement, intensive care unit admission without the need for mechanical ventilation (MV), multisystemic inflammatory syndrome, febrile neutropenia, respiratory distress syndrome, dehydration, and 5) Critical: acute respiratory distress syndrome, respiratory failure requiring MV, shock, encephalopathy, myocardial injury or heart failure, coagulation dysfunction, or acute kidney injury.5,23–25
Contagion waves were defined to compare indicators of COVID-19 mortality in the group of patients diagnosed with leukemia or lymphoma. The case fatality rate was calculated as the ratio of deaths to the total number of cases with leukemia or lymphoma.
To establish the time span of each wave, the curve of confirmed cases was defined according to the date of PCR testing. The start, peak, and end of the curves were determined. The first wave occurred from April 24 (EW 17) to November 18 (EW 47), 2020, with a peak in EW 40; the second wave occurred from December 1 (EW 49), 2020, to October 13 (EW 41), 2021, with a peak in EW 23; and the third wave occurred from December 6 (EW 49), 2021, to February 25 (EW 8), 2022, with a peak in EW 3.