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Metabolic response after intraarterial 90Y-glass microsphere treatment for colorectal liver metastases: comparison of quantitative and visual analyses by 18F-FDG PET.

UNLABELLED
Our aim was to assess the feasibility of using PET for quantifying metabolic response after intraarterial (90)Y-glass microspheres for metastatic colorectal cancer to the liver by comparing visual estimates with hepatic standardized uptake values (SUVs).


METHODS
Twenty-seven patients (15 men, 12 women; age, 68 +/- 12 y [+/-SD]) with metastatic colorectal cancer to the liver, and tumor progression despite polychemotherapy, were included. All patients had baseline CT or MRI, (18)F-FDG PET, hepatic angiography, and intraarterial (99m)Tc-labeled macroaggregated albumin scanning. Patients were treated with (90)Y-glass microspheres and were monitored for 3 mo using PET and serum carcinoembryonic antigen. The average absorbed dose was 139 +/- 22 Gy. All treatments were performed on a lobar basis. For each case analyzed, regions of interest were drawn along the liver edge to measure SUVs on maximum-intensity-projection (MIP) and resliced axial images. Concomitantly, the visual estimate was graded as +1, 0, -1, -2, or -3 for progression, no change, and mild, moderate, and dramatic improvement at posttreatment PET.


RESULTS
Visual estimates placed 20 patients in the response category (-3 to -1) and 7 patients in the nonresponse category (0 to +1). There was a significant drop in the median SUV on the resliced axial images from 10,455 at baseline to 9,075 after treatment (P = 0.011) for the entire group. The percentage of metabolic response was significantly greater in the response group compared with that of the nonresponse group (-26% +/- 25% vs. +6% +/- 15%, P = 0.004). This correlated significantly with the respective visual estimates (r = 0.75, P < 0.0001). Furthermore, the direction of change agreed in 85% of patients using both methods. There was no significant correlation when the SUV from the simplified MIP images were used in the coronal or sagittal manner.


CONCLUSION
It is feasible to quantify reduction of hepatic tumor metabolism objectively after (90)Y treatment for unresectable metastatic disease to the liver. SUVs of the entire axial slices of liver agree well with subjective visual evaluations. Quantitative PET is a useful technique in the treatment response evaluation of patients after (90)Y-glass microspheres.