Evolution of radiation-induced temporal lobe injury after intensity-modulated radiation therapy in nasopharyngeal carcinoma: a large cohort retrospective study

Abstract

Background: Previous studies have demonstrated conflicting findings regarding the initial MRI patterns of radiotherapy-induced temporal lobe injury (RTLI) and the evolution of different RTLI patterns. The aim of this study was to evaluate the initial MRI pattern and evolution of RTLI in patients with nasopharyngeal carcinoma (NPC) by means of a large cohort study.

Methods: Data of patients with RTLI were retrospectively collected from two hospitals between January 2011 and December 2021. The injured lobes were categorized into three patterns based on initial MRI patterns: isolated white matter lesions (WMLs), isolated contrast-enhanced lesions (CELs), and combined WMLs and CELs. The latency period, MRI appearances, and temporal changes in WMLs and CELs were evaluated.

Results: A total of 913 RTLI patients with 1092 injured lobes were included in this study. The numbers of isolated WMLs, isolated CELs, and combined WMLs and CELs identified at the first MRI detection were 7 (0.6%), 172 (15.8%), and 913 (83.6%), respectively. The evolution of bilateral RTLI was different in the same patient, and that of unilateral RTLI combined with WMLs and CELs also may occur asynchronously. The time intervals from the initial MRI detection of isolated WMLs, isolated CELs, combined WMLs and CELs to the last negative MRI scan were 8.6, 8.9 and 11.0 months, respectively. A significant difference was observed in the time intervals between the three patterns (H = 14.287, P = 0.001). And the time interval was identified as an independent factor influencing the initial MRI pattern of RTLI after Poisson regression (P = 0.002).

Conclusion: Both WMLs and CELs could be the initial and only MRI abnormalities in patients with RTLI. This study is of great significance in accurately diagnosing RTLI early and providing timely treatment options. Additionally, it provides clinical evidence for guidelines on NPC, emphasizing the importance of regular follow-up of NPC patients.

Keywords: Intensity-modulated radiotherapy; Magnetic resonance imaging; Nasopharyngeal carcinoma; Temporal lobe injury.

Fig. 1

Flow-chart showing the study’s exclusion criteria. Note: NPC nasopharyngeal carcinoma, RTLI radiotherapy-induced temporal lobe injury, Hospital A  Hunan Cancer Hospital, Hospital B Sun Yat-Sen University Cancer Center

Fig. 2

A representative example of white matter lesion in bilateral temporal lobes and dose distribution of the treatment target area treated with three‑dimensional radiotherapy. a High intensity in the white matter of bilateral temporal lobes on axial T2-weighted image (curved arrow), b contrast-enhanced lesions on axial postcontrast T1-weighted MR image (curved arrow). Dose line distribution is shown in c (axial) and d (coronal), respectively

Fig. 3

MRIs of a patient with RTLI (46y, M). MRIs of a patient with RTLI (46y, M) with the earliest MRI finding of solid enhanced nodule at 10.87 months after receiving IMRT. Axial T2-weighted image shows slightly high intensity in left temporal lobe (a), and a solid enhanced nodule without cystic necrosis is seen in the inferomedial part of the left temporal lobe on the axial post-contrast T1-weighted image (b) (curved arrow). Note: MRI magnetic resonance imaging, RTLI radiotherapy-induced temporal lobe injury, IMRT intensity-modulated radiotherapy

Fig. 4

MRIs of a patient with RTLI (65y, F). MRIs of a patient with RTLI (65y, F) with the earliest MRI findings of isolated white matter lesion at 15.33 months after receiving IMRT. Axial T2-weighted image shows high intensity in white matter (curved arrow) of the left temporal lobe (a), but no significant enhancement is observed on the axial post-contrast T1-weighted image (b). Note: MRI magnetic resonance imaging, RTLI radiotherapy-induced temporal lobe injury, IMRT intensity-modulated radiotherapy

Fig. 5

Evolution of bilateral temporal lobe brain injury in one patient (55y, M). Review was conducted at 32.50 months after IMRT. Axial T2-weighted image and post-contrast T1-weighted image show high intensity (a) and significant enhancement (b) in white matter of the bilateral temporal lobes (curved arrow). After 10.03 months, the white matter lesion and contrast-enhanced lesion increased in the right temporal lobe but regressed in size in left temporal lobe (c, d) (curved arrow). Note: IMRT intensity-modulated radiotherapy

Fig. 6

Evolution of individual components of unilateral temporal lobe injury in one patient (43y, M). Review was conducted at 13.87 months after IMRT. Axial T2-weighted image and postcontrast T1-weighted image show hyperintense (a) and significant enhancement (b) in white matter of left temporal lobe (curved arrow). After 5.73 months, the white matter lesion significantly regressed (c), but the contrast-enhanced lesion increased (d) (curved arrow). Note: IMRT intensity-modulated radiotherapy