Milan criteria in liver transplantation for hepatocellular carcinoma: An evidence-based analysis of 15 years of experience

Hepatocellular carcinoma (HCC) is the seventh most common cancer worldwide and the third most common cause of cancer-related deaths; the number of new cases per year is approaching 750,000. The magnitude of the incidence of HCC has discouraged any attempts to apply liver transplantation (LT) as the prevailing curative therapy for HCC worldwide because of the limited sources of donated organs (deceased and living donors) and the poor access to sophisticated health care systems in some geographical areas. If these limitations continue to prevail throughout the world, any attempt to significantly reduce HCC-related mortality rates through the application of LT will be delusional. International experiences have confirmed, however, the potential of LT to definitively cure HCC because it presents a unique opportunity to remove both the tumor (HCC is associated with 695,000 deaths per year) and the underlying cirrhosis. Despite its limited access, LT has become the standard of care for patients with small HCCs and the main driving force for alternative strategies offered to patients with intermediate HCCs. In 1996, a prospective cohort study defined restrictive selection criteria that led to superior survival for transplant patients in comparison with any other previous experience with transplantation or other options for HCC. Since then, these selection criteria have become universally known as the Milan criteria (MC) in recognition of their origin. Ever since their adoption in clinical practice, the MC have helped doctors to single out early-stage HCC as a prognostic category of cancer presentation that is amenable to curative treatments. After their implementation, the favorable posttransplant outcomes that were observed in cohort series were so convincing that the MC immediately became the standard of care for early HCC, and further validation by randomized controlled trials (RCTs) was prevented. After the passage of approximately a decade, researchers began to challenge the MC with other proposals designed to capture those patients not meeting the MC who could achieve similar posttransplant survival rates through the expansion of the accepted tumor limits for transplant eligibility. None of these expanded criteria have become the new reference standard for selecting LT candidates with HCC; any broadening of the selection criteria for transplantation is inevitably hampered by severe