Role of fluoro-2-deoxyglucose positron emission tomography-computed tomography in assessing response to targeted therapy in metastatic lung cancers

Receptor-specific therapies are indicated in metastatic lung cancers. Metabolic response assessment of targeted therapy is better than assessing the size. This study is a retrospective analysis, where we compared morphologic and metabolic response of computed tomography (CT) and positron emission tomography (PET). Thirty-one patients (23 males, 8 females with an age range of 42–77 years) with epidermal growth factor receptor (EGFR)-positive metastatic lung cancer on gefitinib, who underwent PET/CT, at baseline and at 4–6 weeks, were assessed by Response Evaluation Criteria In Solid Tumors (RECIST) 1.1 and European Organization for Research and Treatment of Cancer (EORTC) criteria. Concordance between RECIST 1.1 and EORTC was seen in 26 (83.7%) patients. Discordance was seen in 5 (16.3%) patients. In patients with discordance, the results were confirmed by follow-up imaging. Metabolic EORTC criteria changed the disease status from stable disease to partial response (3 out of 5) and progressive disease (2 out of 5) in these five patients. Metabolic criteria using PET/CT could accurately predict response as well as disease progression early in the course of targeted therapy, compared to morphologic criteria. In addition, early metabolic response assessment can predict refractoriness of therapy