Utility of 18F-FDG PET and contrast-enhanced CT scan in the assessment of residual liver metastasis from colorectal cancer following adjuvant chemotherapy.

Background: Neoadjuvant chemotherapy has been successfully used in the treatment of patients with colorectal liver metastases. The selection of patients for surgical resection after chemotherapy still poses a significant clinical challenge. (18)F-FDG PET is a useful tool in the assessment of liver metastases but the data regarding its sensitivity after chemotherapy is scarce. Our aim was to assess the value of this imaging modality in the selection of patients with colorectal liver metastasis for surgery following adjuvant chemotherapy.

Material And Methods: We reviewed the diagnostic performances of (18)F-FDG PET and contrast-enhanced CT scan data from patients with colorectal liver metastases following treatment with chemotherapy. Nineteen patients (12 males, 7 females; median age 61 years; range 41-79) were evaluated. Chemotherapy regimens were: FOLFOX (14 patients), FOLFIRI (3 patients), 5-FU/FA (1 patient) and UFT-irinotecan-oxaliplatin (1 patient). Median time between end of chemotherapy and CT scan was 3.4 weeks, between end of chemotherapy and PET was 5.9 weeks and between end of chemotherapy and surgery was 9.9 weeks. All patients underwent surgery and had histopathological confirmation of liver lesions. Nine patients had segmentectomy, 2 patients had wedge resection, 5 patients had right hepatectomy and 3 patients had explorative laparotomy with liver biopsies.

Results: Data from all 19 patients, comprising 65 liver lesions, were confirmed by histo-pathology. Results on a per-lesion basis showed a sensitivity of 62% for (18)F-FDG PET and 70% for CT scan. A complete agreement between (18)F-FDG PET or CT scan and histology was documented in 5 and 3 patients, respectively. The sensitivity of (18)F-FDG PET was shown to increase for lesions larger than 1 cm (74% vs. 18%).

Conclusions: These results suggest that (18)F-FDG PET and CT scan have sub-optimal sensitivity in the evaluation of colorectal liver lesions after neo-adjuvant chemotherapy, especially for lesions < 1 cm. The combined use of the two imaging techniques does not significantly increase the sensitivity of lesion detection.