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OBJECTIVE Distinguishing tumor recurrence from therapy-induced imaging changes (TIIC) on brain MRI in children treated for primary malignant brain tumors may be challenging. The authors aimed to assess the diagnostic ability of multimodal MRI in differentiating TIIC from tumor recurrence. METHODS The authors retrospectively included children with abnormal supratentorial brain MRI findings after treatment for primary malignant brain tumors (regardless of their localization) with complete resection and radiotherapy. A total of 18 patients with TIIC and 25 patients with tumor recurrence were compared, according to structural, apparent diffusion coefficient (ADC), and arterial spin labeling (ASL) imaging data accrued over time. TIIC were defined by a new MRI scan that was stable for at least 1 year or had regressed, or by histopathology findings in specimens obtained when the anomaly was surgically treated. RESULTS The time interval between completion of radiotherapy and the appearance of abnormal brain MRI findings was significantly shorter in the TIIC group compared with the tumor recurrence group (median 6 vs 35 months; p < 0.001). TIIC appeared as foci of increased T2-weighted signal intensity, without nodule, associated with variable contrast enhancement. Tumor recurrence appeared as a well-defined nodule with intermediate signal intensity on T2-weighted images with nodular contrast enhancement. Relative ADC values were significantly higher in the TIIC group (median 1.43 vs 0.88; p < 0.001). Relative ASL–cerebral blood flow (CBF) values were significantly lower in the TIIC group (median 0.27 vs 0.43; p = 0.04). On follow-up MRI, TIIC could progress, regress, or remain stable. In most instances (72%), they decreased in size or remained stable at 4 years of follow-up. CONCLUSIONS MRI features of TIIC include foci of increased signal intensity without a demonstrable nodule on T2-weighted images, high ADC values, and lower ASL-CBF values, whereas tumor recurrence appears as a well-defined nodule with low ADC values and higher ASL-CBF values.

Objectives To assess the sensitivity of two secondary electronic sources of COVID-19 studies: 1) the Cochrane COVID-19 Study Register ( https://covid-19.cochrane.org/ ); and, 2) the Living Overview of the Evidence (L•OVE) COVID-19 platform ( https://iloveevidence.com/ ). Study design and setting We identified reports of randomized controlled trials (RCTs) and observational studies (OS) assessing preventive interventions or treatment for COVID-19. The reference standard comprised all reports included in the COVID-NMA platform (covid-nma.com), in two major living systematic reviews of RCTs assessing pharmacologic treatment of COVID-19, or identified in either of the two secondary sources evaluated. The search for all sources was conducted through September 7, 2020. Our primary outcome was the proportion of the reports included in the reference standard that were identified by each secondary source. Results We identified 680 reports, 91 RCT reports, 97 RCT protocols, and 492 OS reports. The Cochrane COVID-19 Study Register identified 88% [95% confidence interval, 79–94] of the RCT reports, 90% [82–95] of the RCT protocols, and 82% [78–85] of the OS reports. The L•OVE platform identified 100% [97–100] of the RCT reports and RCT protocols and 100% [99–100] of the OS reports. Conclusion These platforms proved to be a viable screening alternative to searching every individual source.