Abstracts
1997 Digestive Disease Week

Preoperative mapping with MRI predicts complete ablation by cryosurgery in patients with hepatic metastases.

LB Johnson, TS Krebs, JJ Wong, B Daly, PC Kuo, JS Plotkin, M Njoku, D Van Echo. University of Maryland School of Medicine, Baltimore, MD.

Cryosurgery extends the surgical options for patients with hepatic metastases. Selection for cryosurgery includes unresectable lesions less than 6 cm. in size and is generally limited to less than 6 total lesions. More importantly, the position of lesions away from major hepatic veins or major branches of the portal vein predicts complete ablation with cryosurgery. Preoperative mapping of metastases with magnetic resonance imaging (MRI) can demonstrate proximity to major vessels which will serve as "heat sinks" and prevent complete necrosis of the metastasis. We retrospectively reviewed the preoperative MRI or computed tomography of patients who underwent cryosurgery from 12/94 to 12/96. Metastases were identified and mapped for any border less than 1 cm. from a major hepatic vein or branch of the portal vein. Data are expressed as mean ± SEM. Statistical analysis was performed with Fisher Exact test or Mann-Whitney Rank Sum test, as appropriate. Forty-seven patients were referred for cryosurgery between 12/94 and 12/96. Thirteen patients were selected for cryosurgery. Eight of these patients underwent combined cryosurgery and hepatic resection. A total of 19 lesions were ablated with cryosurgery. Eight lesions were within 1 cm of a major portal vein branch or hepatic vein. All eight (100%) of these lesions were incompletely ablated, while 7 of 8 lesions greater than 1 cm from a major hepatic vessel were completely ablated, as determined by intraoperative ultrasound and postoperative MRI.

                   Size          Predicted   Confirmed     Incomplete
                   (CM)          by MRI      intraop U/S   ablation
 Lesions < 1 cm    5.25 ±0.4#    8           8             8/8 (100%)*
 Lesions > 1 cm    2.31 ±0.3     8           8             1/8 (12%)
 # P < 0.01 vs. Lesions > 1 cm., * P > 0.01 vs. Lesions < 1 cm.

Conclusions; 1) Incomplete ablation commonly occurs in lesions that encroach within 1 cm of major branches of the hepatic veins or portal vein. 2) Preoperative mapping of metastases can predict ability for complete ablation. 3) Combined hepatic resection with cryosurgical ablation may be a preferred modality for patients with limited bilobar disease with metastases that encroach upon major hepatic vessels.