S813
Clinical - Lung
ESTRO 2026
Mini-Oral 3235
No PCI, No Escape: MRI Surveillance Reveals Silent Brain Metastases in SCLC – A Multicenter Cohort Ismaell Massalha 1,2 , Nashat Abu Yasin 2 , Adham Hijab 1 , Yonina Tova 1 , Konstantin Lavrenkov 2 1 Radiation oncology, Rivka Ziv Medical Center, Tzfat, Israel. 2 The Legacy Heritage Cancer Center, Dr. Larry Norton Institute, Soroka Medical Center, Beer-Sheva, Israel Purpose/Objective: In small-cell lung cancer (SCLC), brain metastases (BM) develop in up to 50% of patients within two years despite chemotherapy. Prophylactic cranial irradiation (PCI) reduces BM incidence but provides no overall- survival (OS) advantage and carries neurocognitive risks. This study evaluated whether routine brain-MRI surveillance, in the absence of PCI, enables earlier detection of occult BM and influences clinical outcomes. Material/Methods: Retrospective multicenter cohort of 189 consecutive SCLC patients (2015–2025) from two Israeli institutions; none received PCI. Adherence was defined as ≥ 2 brain MRIs at ≤ 6-month intervals after the staging MRI in BM-free cases. Endpoints included time-to-BM, progression-free survival (PFS), and OS. Death without BM was treated as a competing risk (Fine-Gray). Multivariable Cox models adjusted for age, performance status (PS), stage, Charlson Comorbidity Index (CCI; auto-derived), and geographic distance. Sensitivity analyses: 60-day landmark and 1:1 propensity-score matching (PSM). Power = 80% for HR = 2.0 ( α = 0.05, 47 events). Proportional-hazards assumption verified (Schoenfeld p > 0.05). Results: Median age 68 y; 52% limited stage; 68% PS 0–1; median CCI = 2. Adherence rate 19% (36/189).Twelve- month BM incidence: 28% (adherent) vs 12% (non- adherent), Gray p = 0.002.Fine-Gray HR 4.15 (95% CI 2.28–7.55, p < 0.001); Cox HR 3.49 (95% CI 1.90–6.44, p < 0.001).PSM confirmed significance: HR 3.88 (95% CI 1.78–8.46, p = 0.001; n = 72 pairs).CCI modified effect: HR 4.2 (high CCI) vs 2.8 (low CCI).No survival improvement: PFS HR 0.95 (p = 0.80); OS HR 1.07 (p = 0.82).Median post-radiotherapy intracranial control = 8 months, unaffected by adherence (log-rank p = 0.42).Landmark analysis confirmed the absence of immortal-time bias.
Conclusion: In this PCI-free SCLC cohort, MRI surveillance tripled BM detection, particularly among high-CCI patients, but did not improve PFS or OS, suggesting lead-time bias. These findings question the utility of routine 3–6- month MRI surveillance in low-risk patients and support a risk-adapted strategy focusing on high-CCI or poor-PS subsets. Prospective trials should assess neurocognitive trade-offs and cost-effectiveness. References: -Taylor JM, Rusthoven CG, Moghanaki D. Prophylactic cranial irradiation or MRI surveillance for extensive stage small cell lung cancer. J Thorac Dis. 2020 Oct;12(10):6225-6233. doi: 10.21037/jtd.2020.03.80. PMID: 33209461; PMCID: PMC7656401.- Prophylactic Cranial Irradiation for Small-Cell Lung Cancer: Time for a Reassessment. Am Soc Clin Oncol Educ Book 40, 24- 28(2020).DOI:10.1200/EDBK_281041- Prophylactic Cranial Irradiation for Extensive Small-Cell Lung Cancer. JOP 13, 732-
738(2017).DOI:10.1200/JOP.2017.026765 Keywords: Occult Brain Metastases, SCLC
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