Foundations · Year 1 · from Foundations
Case 3: FDG-PET Positive Lung Mass (Warburg Effect)
Clinical Image
Source: Radiopaedia - Lung cancer FDG PET - CC BY-NC-SA 3.0
Case Presentation
A 62-year-old man with a 40 pack-year smoking history presents with a 3-month history of cough and unintentional 15-pound weight loss. Chest CT reveals a 4 cm spiculated mass in the right upper lobe with mediastinal lymphadenopathy. For staging, an FDG-PET scan is performed. The scan shows intense uptake (SUV max 12.5) in the primary lung mass and multiple mediastinal lymph nodes, but no distant metastases. CT-guided biopsy confirms non-small cell lung cancer (adenocarcinoma). The patient asks why the PET scan "lights up" cancer. He is explained that cancer cells preferentially use glycolysis even in the presence of oxygen (the Warburg effect), consuming glucose at high rates. The radiotracer 18F-fluorodeoxyglucose (FDG) is taken up by glucose transporters and phosphorylated by hexokinase but cannot proceed further in glycolysis, so it becomes trapped and accumulates in metabolically active cancer cells. He is referred to oncology for treatment of stage IIIA disease.
Key Learning Points
- The Warburg effect describes the preference of cancer cells for glycolysis even when oxygen is available (aerobic glycolysis), producing lactate rather than fully oxidizing glucose
- While seemingly inefficient (2 ATP vs. 30-32 ATP per glucose), this metabolic reprogramming supports rapid proliferation by diverting glycolytic intermediates to biosynthetic pathways for nucleotides, amino acids, and lipids
- FDG-PET exploits the Warburg effect: FDG is trapped after hexokinase phosphorylation in cells with high glycolytic activity, allowing visualization of tumors, staging, and monitoring treatment response