Background: OLT is the definitive treatment for HCC. Vascular invasion, tumor size, and proliferation are known risk factors for recurrence post-OLT. Undetected lesions <1cm are considered incidental findings, and not risk factors. This study reviews possible risk factors related to recurrence and mortality. Methods: A retrospective evaluation of 164 patients undergoing OLT for HCC from '07-'12 was performed. T1/T2-weighted MRIs within 90 days of OLT were compared to explants.Lesion size, number and degree of invasion were reviewed. Post-OLT CT/MRI studies were screened for HCC. Groups with/without undetected lesions found on pathology were compared for risk factors. Results: Prospective MRI interpretation with/without contrast (gadolinium/Eovist) revealed 223 HCCs in 164 patients, 1.40 per patient. Pathology demonstrated 518 lesions (3.16 per patient). MRI sensitivity for any lesion was 44%, 229/518. Sensitivity for lesion detection <1cm was only 7.53%, 11/146. Severity was understated prior to explant, with 31.1%, 51/164 demonstrating microvascular invasion vs. 2.4%, 4/164 with macrovascular invasion. Recurrent HCC was 20.7%, 34/164 patients. 16 biopsy proven, and 18 diagnosed by imaging. Median recurrence interval was 16 mos. 25 patients expired after OLT; many of them from recurrent HCC. In this subset, 66.4%, 71/107 lesions were undetected pre-OLT MRI. 60%, 15/25 deceased patients had vascular invasion, 2 macrovascular. 53%, 8/15 with microvascular invasion developed metastatic HCC. MRI failed to detect 1.75 lesions/patient in this subgroup. Discussion: MRI underestimates the number and overall tumor burden. Data demonstrates that 44% of lesions were identified on pre-OLT MRI (7.53% of lesions <1cm). A comparison was made in patients with/without undetected lesions to determine risk factors for invasion, recurrence and mortality. The mortality secondary to recurrence post-OLT is significant in HCC patients with microvascular invasion. Rates of invasion, recurrence and mortality with/without undetected lesions are 47.5%, 25.0% and 23.8% vs. 28.4%, 20.9% and 10.4% respectively. Conclusion: Pre-OLT MRI has poor sensitivity in defining lesions <1cm. Incidence of microvascular invasion is higher, 47.5% vs. 28.4%, when undetected lesions are found. Invasion is a known cause for recurrence. Presence of lesions <1cm demonstrates higher recurrences rates 25.0% vs. 20.9% and appears to be clinically important. A more than twofold increased mortality rate 23.8% vs. 10.4% was seen.

Teperman, L.: Grant/Research Support, Onyx/Bayer.

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