The largest randomized controlled trial (RCT) on the effect of FDG-PET on surgical management for metastatic colorectal adenocarcinoma to liver ("PET-CAM") reported only a modest change in surgical management (8%).
Purpose: To explore the relationship between prior chemotherapy and detection of metastatic disease on PET in patients from PET-CAM. Secondary aim: to determine whether centralized imaging interpretation could have impacted trial results.
Methods: The study included 120 patients from a single institution. Local PET interpretation (PET-L) was recorded from the original database. Retrospective PET interpretation was performed independently by at least one additional reader (PET-C). The presence of extrahepatic disease (EHD) and significant additional liver metastases (=SALM), defined as metastases not originally planned for resection, was recorded. Patients were stratified to responders to recent chemotherapy (Group R) versus all others (Group O) according to surgical pathology and RECIST criteria.
Results: Thirty-seven of 50 patients who received recent chemotherapy (<90 days) were responders (Group R). EHD was present in 30/120 (25%) patients. There was no difference in detection of EHD on PET-L (7/37;18.9%), PET-C (7/37;18.9%), and CT (4/37;10.8%) for Group R (p = 0.375), but in Group O more EHD was detected on both PET-L (15/83;18.1%) and PET-C (22/83;26.5%) than CT (8/83;9.6%); p = 0.039 and p < 0.001, respectively. For the entire cohort, PET-L and PET-C detected EHD and/or SALM not reported on CT in 14 (11.7%) and 22 (18.3%) patients.
Conclusion: The impact of recent chemotherapy on detection of colorectal metastases with PET suggests that the utility of PET in patient selection for liver resection in the prior PET-CAM-RCT may have been underestimated.
Keywords: Chemotherapy; Colorectal cancer; FDG; Liver metastases; PET.