Enhancement patterns of colorectal liver metastases on pre-sirt mapping CT arteriography correlates with FDG-PET SUVmax metabolic response

To evaluate if arterial enhancement patterns of colorectal liver metastases (CLM), as noted during pre-SIRT mapping hepatic CT arteriography, correlate with FDG-PET SUVmax metabolic response after SIRT A retrospective review of a prospectively created HIPAA-compliant SIRT database was performed. All patients with CLM and available PET scans at baseline and post-SIRT were included. During arteriography mapping, a CT arteriogram was obtained 4-6 seconds after contrast injection directly into hepatic artery branches at a rate of 0.5-3 cc/sec. Images were reviewed by two independent observers blinded to metabolic tumor response. Tumors were classified into 3 categories: enhancing, enhancing margin/nodule, and non-enhancing. Interobserver agreement was assessed with kappa statistic. ANOVA compared the mean percentage change in SUVmax between categories. Fischer’s exact test compared the percentage of lesions within each category showing: (a) any decrease and (b) ≥ 25% decrease in SUVmax. The study enrolled 31 patients with 80 target lesions: median of 3 target lesions per patient (range: 1-6). A moderate to substantial interobserver agreement of arterial enhancement classification was noted (kappa value: 0.62). Discrepancies were reviewed to reach a consensus. Tumors were classified as: enhancing (48/80) (60%), enhancing margin/nodule (19/80) (24%), and non-enhancing (13/80) (16%). The mean percentage change in SUVmax post SIRT was - 35% (+/-24%) for enhancing lesions, - 19% (+/- 38%) for lesion with enhancing margin/nodule, and + 25% (+/- 40%) for non enhancing lesions (P<0.001). SUVmax decreased in 94% (45/48) of enhancing lesions, 79% (15/19) of lesions with enhancing margin/nodule, and in only 23% (3/13) of non-enhancing lesions (P<0.001). A ≥ 25% decrease in SUVmax was observed in 75% (36/48) of enhancing lesions, 53% (10/19) of lesions with enhancing margin/nodule, and 23% (3/13) of non-enhancing lesions (3/13) (P=0.002). The majority of CLM showed an enhancement pattern on mapping CT arteriography. Enhancement on mapping CT arteriography is a significant predictor of metabolic response on the 1st FDG-PET following SIRT for CLM.