18F-FDG PET (PET) does not improve CT scan (CT) accuracy in the evaluation of colorectal cancer liver metastases after chemotherapy

Abstract

13530 Background: Neoadjuvant chemotherapy has been successfully used in the treatment of patients (pts) affected by liver metastases from colorectal cancer unsuitable for surgery. We evaluated separately the diagnostic accuracy of PET and CT in this setting in a small series of pts. Methods: We retrospectively reviewed the data from 19 consecutive pts (12 males, 7 females; median age 62 years; range 41–79) affected by liver metastases from colorectal cancer. All of the pts underwent systemic chemotherapy and were evaluated with PET and CT at the end of the treatment. Whole-body PET scan was performed in 3D mode on a Siemens Ecat Accel LSO full-ring scanner, 60 minutes after the injection of 310–450 MBq of 18F-FDG. Contrast enhanced, 3 phases, liver CT was performed on a Philips Aura single slice system. Chemotherapy regimens were: FOLFOX (13 pts), FOLFIRI (2 pts), 5-FU-FA (2 pts), UFT-CPT-OXA (2 pts). Overall response rate was 68%. Median time interval between end of chemotherapy and CT was 6 wks (range 3–8), between end of chemotherapy and PET was 8 wks (range 5–13) and between end of chemotherapy and surgery was 10 wks (range 6–18). All pts underwent surgery to remove liver metastases and had histological confirmation of the lesions. Results: In 16 evaluable pts, 53 liver lesions were confirmed by histology. The table shows the results on a per-lesion basis. A complete agreement between PET or CT and histology was documented in 3 and 4 pts respectively. Conclusions: These results suggest that PET and CT had sub-optimal diagnostic accuracy in the post-chemotherapy evaluation of liver lesions from colorectal cancer. Moreover, the combined use of the two imaging techniques does not significantly increase the sensitivity of CT. Further data are needed to evaluate the metabolic changes induced by chemotherapy which may be the cause for inaccurate PET findings. [Table: see text] No significant financial relationships to disclose.