Assessing Early Vascular Changes and Treatment Response After Laser-Induced Thermotherapy of Pulmonary Metastases With Perfusion CT: Initial Experience

The objective of our study was to use perfusion CT to prospectively monitor early vascular changes in tumor perfusion of pulmonary metastases after laser-induced thermotherapy (LITT) and to determine whether any of the perfusion parameters would predict technical success after therapy.Twelve patients with histologically proven pulmonary metastases undergoing LITT were enrolled prospectively in this study. Perfusion CT was performed before treatment, 1 day after treatment, and 4-6 weeks after therapy, and tumor blood flow, tumor blood volume (TBV), mean transit time (MTT), and permeability of the capillary wall surface (capillary permeability-surface product) in 22 pulmonary metastases were calculated. Perfusion parameters at baseline and after LITT were compared. Measurement of tumor diameter on long-term follow-up CT was the gold standard with which perfusion CT results were compared for local control.Median tumor blood flow, TBV, and capillary permeability-surface product had decreased significantly from baseline by 43%, 61%, and 73%, respectively, 1 day after LITT. Perfusion parameters obtained 4-6 weeks after treatment had not changed significantly compared with those obtained 1 day after therapy. There seems to be a good correlation between changes in perfusion CT parameters 1 day after therapy and local outcome, according to the Response Evaluation Criteria in Solid Tumors (RECIST), 1 year after therapy.Perfusion CT of pulmonary metastases has potential in the assessment of early vascular changes that result from LITT and predicting technical success immediately after treatment. Tumors with perfusion measurements that had not changed after therapy indicated progressive disease.