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Published on: December 28, 2017
Metabolic Tumor Volume as a Predictor of Benefit From Prophylactic Cranial Irradiation in Limited-Stage Small Cell
Taejun Lee1, Chang Gon Kim1, Kyung Hwan Kim2
11Division of Medical Oncology, Department of Internal Medicine, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, Republic of Korea.
Background:
Prophylactic cranial irradiation (PCI) reduces the incidence of brain metastases (BMs) in patients with limited-stage small cell lung cancer (LS-SCLC). However, predictive biomarkers that identify patients most likely to benefit from PCI have not been established. This study investigates the potential of 18F-fluoro-2-deoxyglucose (18F-FDG) PET as a predictor of PCI benefit in patients with LS-SCLC.
Patients And Methods:
This multicenter study analyzed patients with LS-SCLC who underwent brain MRI and 18F-FDG PET/CT at baseline, followed by treatment with concurrent chemoradiotherapy. To evaluate whether the benefit of PCI varies according to BM risk, we compared outcomes between PCI-treated and untreated patients stratified by risk group.
Results:
Of 261 patients overall, 171 received PCI and 90 did not. In patients not receiving PCI, high metabolic tumor volume (MTV; >45.201 cm3) was associated with inferior intracranial time to progression (iTTP; hazard ratio [HR], 5.62; 95% CI, 1.69-18.77; P=.005), progression-free survival (PFS; HR, 2.35; 95% CI, 1.38-4.02; P=.002), and overall survival (OS; HR, 2.23; 95% CI, 1.27-3.91; P=.005). Conversely, MTV demonstrated no significant association with survival outcomes among PCI recipients. Subgroup analysis revealed that PCI conferred no survival advantage in the low-MTV group, whereas in the high-MTV group, PCI was associated with improved iTTP (HR, 0.27; 95% CI, 0.15-0.51; P<.001), PFS (HR, 0.49; 95% CI, 0.35-0.69; P<.001), and OS (HR, 0.56; 95% CI, 0.40-0.80; P=.001). Interaction analysis confirmed a significant effect modification between MTV status and PCI benefit for iTTP, PFS, and OS, supporting MTV as an independent predictive biomarker for PCI benefit.
Conclusions:
Baseline PET-derived MTV serves as a clinically relevant predictor of PCI benefit in LS-SCLC, supporting a risk-adapted PCI strategy guided by metabolic imaging biomarkers. This approach may reduce unnecessary neurotoxicity and optimize treatment outcomes and should be prospectively validated.
