Fig. 1
a Chest CT image at baseline. b Chest CT image after 2 cycles of platinum-based doublet chemotherapy (PT-DC). c Chest CT image after 5 cycles of PT-DC. d 4DST PET/CT image at baseline. e 4DST PET/CT image after 2 cycles of PT-DC. f FDG PET/CT image at baseline. g FDG PET/CT image after 2 cycles of PT-DC. Chest CT image at baseline shows lung lesion with a diameter of 55 mm in the right lower lobe (a), with intense uptake of both FDG (f) (SUVmax 15.8, MTV 81.0, TLG 672.5) and 4DST (d) (SUVmax 4.7, MTV 13.6, TLP 42.1). After 2 cycles of PT-DC, the diameter of lung cancer has decreased to 22 mm (b), categorized as partial response based on RECIST. However, 4DST uptake and uptake area were increased after 2 cycles of PT-DC (e) (SUVmax 4.9, MTV 18.2, TLP 56.4) compared to baseline 4DST PET/CT (d). FDG uptake and uptake area were decreased after 2 cycles of PT-DC (g) (SUVmax 7.0, MTV 25.0, TLG 86.4), categorized as partial metabolic response based on EORTC and PERCIST. After 5 cycles of PDC, the lung lesion showed regrowth with a diameter of 30 mm (c), indicating recurrence. Recurrence could be predicted earlier with 4DST PET/CT than with chest CT or FDG-PET/CT