Response evaluation after immunotherapy in NSCLC: Early response assessment using FDG PET/CT

Area of Science:

• Oncology
• Nuclear Medicine
• Radiology

Background:

• Immune checkpoint inhibitors (ICIs) have revolutionized non-small cell lung cancer (NSCLC) treatment.
• Accurate early assessment of treatment response is crucial for optimizing patient management.
• Fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) is a key imaging modality for evaluating metabolic activity.

Purpose of the Study:

• To evaluate the role of early FDG PET/CT in predicting treatment outcomes for NSCLC patients receiving ICIs.
• To assess tumor response using standardized criteria (PERCIST and EORTC) after initial ICI cycles.
• To correlate imaging findings with clinical benefit and progression-free survival.

Main Methods:

• Retrospective analysis of 24 NSCLC patients treated with nivolumab or pembrolizumab.
• FDG PET/CT scans performed after 2-3 cycles (SCAN-1) and later (SCAN-2) of ICI treatment.
• Tumor response assessed by PERCIST and EORTC criteria; clinical benefit and progression-free survival analyzed.

Main Results:

• Early assessment revealed Complete Metabolic Response (CMR) in 4, Partial Metabolic Response (PMR) in 1, Progressive Metabolic Disease (PMD) in 14, and Stable Metabolic Disease (SMD) in 4 patients.
• CMR or PMR at SCAN-1 correlated with clinical benefit.
• Metabolic parameters (peak standardized uptake value, metabolic tumor volume) were significant predictors of progression (HRs 1.18 and 1.00).
• Patients with PMD showed no clinical benefit; SMD patients had variable outcomes requiring careful follow-up.

Conclusions:

• Early FDG PET/CT metabolic parameters can predict post-ICI treatment progression in NSCLC.
• While CMR, PMR, and PMD are reliably assessed, SMD requires meticulous follow-up due to inconsistent clinical benefits.
• FDG PET/CT is valuable for early response assessment in NSCLC patients on ICI therapy.