P26.01 Detecting Oligo-Metastatic/Progressive Disease in Advanced EGFR-Mutant NSCLC: PET/CT and Conventional Imaging Methods

Abstract

Local ablative therapy (LAT) could potentially prolong patient's survival in advanced EGFR-mutant non-small cell lung cancer (NSCLC) receiving first-line EGFR tyrosine kinase inhibitors (TKIs) and harboring oligo-metastatic/progressive (OMD/OPD). However, the exact frequency of OMD/OPD and the optimal imaging method for identifying patients with OMD/OPD remain controversial. Consecutive cases with first-line EGFR-TKI treated metastatic EGFR-mutant NSCLC were retrospectively screened and those receiving PET/CT or complete conventional imaging methods (CIM), including brain MRI, chest CT, abdomen ultrasound or CT and bone scintigraphy, at baseline were included. OMD/OPD was defined as metastases/progressions documented at a maximum of 5 lesions (all thoracic lymph nodes as one lesion) and 3 organs, otherwise was referred to as multiple-metastatic/progressive disease (MMD/MPD). OMD was detected in 53 (22.7%) of 233 patients evaluated by PET/CT and 29 (18.2%) of 159 patients evaluated by CIM at baseline. Among the patients evaluated with baseline PET/CT, time to treatment failure (TTF) tended to be longer in patients with OMD than those with MMD (p=0.061) and concurrent LAT significantly prolonged TTF in patients with OMD (28.0 vs 18.1 months, p=0.027). However, this was not the case among the patients evaluated with baseline CIM. With a median follow-up of 24.2 (range, 1.1-117.6) months, initial disease progression (FPD) was documented in 297 patients, 147 (49.5%) of whom had adequate imaging scans to comprehensively analyze the tumor distributions at FPD. OPD was detected in 23 (62.2%) of the 37 patients evaluated by PET/CT at both baseline and FPD (PET/CT group), 16 (39.0%) of the 41 patients evaluated by CIM at both baseline and FPD (CIM group), and 23 (33.0%) of the 69 patients evaluated by PET/CT at baseline and CIM at FPD (PET/CT-CIM group), respectively. The post-progression overall survival (OS2) was significantly longer for patients with OPD than those with MPD (p=0.032) in the PET/CT group, but was similar in the other two groups. Disease progression only at the originally existed sites (original PD) was detected in 43.2%, 26.8% and 65.2% of patients with FPD in the PET/CT, CIM and PET/CT-CIM group, respectively. Patients with only original PD had significantly longer OS2 (p=0.004) in the PET/CT group, but was not the case in the other two groups. PET/CT has better performance in detecting OMD/OPD in first-line EGFR-TKI treated advanced EGFR-mutant NSCLC. Patients with PET/CT-detected OMD may benefit from appropriate LATs.