Pre-treatment FDG-PET predicts the site of in-field progression following concurrent chemoradiotherapy for stage III non-small cell lung cancer

• Thoracic failure after definitive chemoradiotherapy for NSCLC is common.
• PET may predict outcomes as well as the sites of disease progression.
• High patient MTV was associated with an increased risk of disease progression.
• Progression nearly always occurred in lesions with high MTV.

PurposeLocoregional progression following definitive chemoradiotherapy (CRT) for locally advanced non-small cell lung cancer (NSCLC) is common. In this study, we explore the utility of pre-treatment PET for predicting sites of disease progression following CRT.MethodsWe identified patients treated at our institution with definitive, concurrent CRT for stage III NSCLC in the years 2007–2010 who underwent staging FDG-PET/CT. Using a semiautomatic gradient-based tool, visible thoracic hypermetabolic lesions were contoured on each patient's pre-treatment PET. Post-treatment imaging was reviewed to identify specific locations of disease progression.Patients’ maximum SUV (SUVmax_pat) and metabolic tumor volume (MTV_pat) were evaluated as predictors of clinical outcomes using logrank testing. Competing risks analysis was performed to examine the relationship between lesion (tumor or lymph node) MTV (MTV_les) and the risk of local disease progression. Patient death and progression in other sites were treated as competing risks.Results28 patients with 82 hypermetabolic lesions (27 pulmonary tumors, 55 lymph nodes) met inclusion criteria. Median follow-up was 39.0 months for living patients. Median progression-free survival (PFS) was 12.4 months, and median overall survival (OS) was 31.8 months. Low MTV_pat was associated with improved PFS (median 14.3 months for MTV < 60 cc vs. 9.7 months for MTV > 60 cc, p = 0.039).MTV_les was strongly associated with the risk of local disease progression. The 2-year cumulative incidence rate (CIR) for progression in lesions larger than 25 cc was 45%, compared to 5% for lesions under 25 cc (p < 0.001).ConclusionPre-treatment PET can be used to identify specific lesions at high risk for treatment failure following definitive CRT for locally advanced NSCLC. Selective treatment intensification to high-risk lesions should be studied as a strategy to improve clinical outcomes in this patient population.