Clinical and Magnetic Resonance Findings for the Diagnosis of Recurrent Tumors versus Radiation-Induced Secondary Tumors of Malignant Pediatric Brain Tumors of the Posterior Fossa.

Abstract

Irradiation is one of the main therapeutic strategies used to treat patients with malignant pediatric brain tumors of the posterior fossa (MPBTPFs). Any recurrent intracranial lesion that forms after treatment completion is either a radiation-induced secondary tumor (RIST) or a recurrent tumor (RT), and patients with these tumors have similar presentations. The aim of our study was to diagnose RIST and RT on the basis of their clinical and magnetic resonance imaging (MRI) features to guiding optimal treatment strategies. From 2003 to 2022, we retrospectively enrolled 20 MPBTPF patients with pathologically confirmed RIST after complete surgery and irradiation. We also enrolled 20 MPBTPF patients with RTs with matched primary tumor types and evaluated the clinical and MRI findings and outcomes of these patients. The latency period was significantly longer in RISTs than in RTs (152.5 vs. 22 months, P < 0.001). None of the RISTs arose from the primary surgical bed or exhibited leptomeningeal seeding. Benign RISTs tended to be well-defined and showed homogeneous enhancement. In contrast, malignant RISTs largely resembled RTs morphologically but demonstrated larger tumor volumes and higher apparent diffusion coefficient (ADC)_min and ADC ratios (all P < 0.05). Receiver operating characteristic analysis revealed that latency was the strongest discriminator between malignant RISTs and RTs (area under the receiver operating characteristic curve [AUC] = 0.90), followed by tumor volume (AUC = 0.81), ADCmin (AUC = 0.76), and ADC ratio (AUC = 0.72) CONCLUSIONS: In patients with MPBTPF who undergo surgery and radiotherapy, RISTs can be distinguished from RTs by clinical and MRI features, which may help guide early treatment planning.