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. 2025 Apr 1;50(4):281-288.
doi: 10.1097/RLU.0000000000005703. Epub 2025 Feb 17.

Prognostic Value of 18 F-FDG PET in Primary Central Nervous System Lymphoma : Assessing Interim Metabolic Response for Improving Patient Stratification

Ga-Young Song  1 , Ho Cheol Jang  1 , Mihee Kim  1 , Seo-Yeon Ahn  1 , Sung-Hoon Jung  1 , Jae-Sook Ahn  1 , Je-Jung Lee  1 , Hyeoung-Joon Kim  1 , Jang Bae Moon  2 , Su Woong Yoo  2 , Seong-Young Kwon  2 , Jung-Joon Min  2 , Hee-Seung Bom  2 , Sae-Ryung Kang  2 , Deok-Hwan Yang  1
Affiliations

Prognostic Value of 18 F-FDG PET in Primary Central Nervous System Lymphoma : Assessing Interim Metabolic Response for Improving Patient Stratification

Ga-Young Song et al. Clin Nucl Med. .

Abstract

Purpose of the report: The usefulness of brain 18 F-FDG PET/CT in primary central nervous system lymphoma (PCNSL) remains underexplored. This study investigated whether early metabolic responses in interim brain FDG PET/CT serve as a prognostic indicator of PCNSL treatment outcomes.

Patients and methods: This prospective study included 53 patients with PCNSL who underwent a high-dose methotrexate-based treatment. Brain FDG PET was performed at diagnosis (baseline PET) and after induction chemotherapy (interim PET), assessing interim PET parameters such as the highest maximum standardized uptake value (hSUV max ), sum of SUV max (sumSUV max ), highest tumor-to-normal ratio (hTNR max ), sum of TNR max (sumTNR max ), highest metabolic tumor volume (MTV) (hMTV), and sum of MTV (sumMTV) across all PET-positive lesions.

Results: High interim hTNR max (hazards ratio: 9.76, 95% confidence interval: 1.90-50.11, P = 0.01) was an independently significant predictor of poor progression-free survival in multivariate analysis. Patients with low interim hTNR max (≤1.0) had a significantly longer median progression-free survival than those with high interim hTNR max (>1.0) (25.0 vs 3.6 months, P < 0.001). Incorporating interim MRI-based clinical response assessments and hTNR max allowed the classification of partial response subgroups with markedly different prognoses ( P < 0.001). High interim hTNR max (hazards ratio: 2.76, 95% confidence interval: 1.39-5.48, P = 0.004) was an independently significant predictor of poor overall survival in multivariate analysis.

Conclusions: The hTNR max measurement from interim brain FDG PET scans emerges as an important prognostic marker in PCNSL. These findings underscore the potential of interim FDG PET evaluations to refine response assessments and inform tailored therapeutic strategies.

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Conflict of interest statement

Conflicts of interest and sources of funding: none declared. This study was supported by grants from the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health and Welfare, Republic of Korea (HR20C0021) and the Chonnam National University Hwasun Hospital Research Institute of Clinical Medicine (HCRI22009 and HCRI23001). This study was also supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government (MSIT) (NRF-2022R1F1A1072352).

Figures

FIGURE 1
FIGURE 1
Measurement of the SUVmax and TNRmax for PET-positive lesions. To assess interim FDG uptake within tumors, a spherical VOI (blue right circle) encompassing the entire tumor was drawn on the interim brain PET images. For reference, additional spherical VOI (blue left circle) was drawn in the contralateral homologous normal brain. The SUVmax within these VOIs was recorded for both tumors and the reference area. The TNRmax for each PET-positive lesion was calculated as the ratio between the tumor and reference SUVmax.
FIGURE 2
FIGURE 2
Kaplan-Meier analyses of (A) PFS and (B) OS according to an interim hTNRmax cutoff of 1.0 in all patients.
FIGURE 3
FIGURE 3
Kaplan-Meier analyses of PFS and OS according to interim MRI-based clinical response assessment (A and B) and incorporating interim MRI-based clinical response assessment and the interim hTNRmax in patients achieving interim clinical PR (C and D).
FIGURE 4
FIGURE 4
Representative cases. Patients achieving PR on interim MRI showed different prognosis according to the results on interim 18F-FDG PET/CT. The patients with hTNRmax ≤ 1.0 on interim PET/CT (A and B) showed longer PFS and OS than the patients with hTNRmax > 1.0 (C and D).
See this image and copyright information in PMC

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