Predicting the probability of progression-free survival in patients with small hepatocellular carcinoma

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Abstract
Allocation of cadaveric livers to patients based on such objective medical urgency data as the Model for End-Stage Liver Disease (MELD) score may not benefit patients with small hepatocellular carcinomas (HCCs). To ensure that these patients have a fair opportunity of receiving a cadaveric organ, the risk for death caused by HCC and tumor progression beyond 5 cm should be considered. Using a Markov model, two hypothetical cohorts of patients with small hepatomas were assumed to have either (1) Gompertzian tumor growth, in which initial exponential growth decreases as tumor size increases; or (2) rapid exponential growth. The model tracked the number of patients who either died or had tumor progression beyond 5 cm. These results were used to back-calculate an equivalent MELD score for patients with small HCCs. All probabilities in the model were varied simultaneously using a Monte Carlo simulation. The Gompertzian growth model predicted that patients with a 1- and 4-cm tumor have 1-year progression-free survival rates of 70% (HCC-specific MELD score 6) and 66% (HCC-specific MELD score 8), respectively. When assuming rapid exponential growth, patients with a 1- and 4-cm tumor have progression-free survival rates of 69% (HCC-specific MELD score 6) and 12% (HCC-specific MELD score 24), respectively. Our model predicted that the risk for death caused by HCC or tumor progression beyond 5 cm should increase with larger initial tumor size in patients with small hepatomas. To ensure that these patients have a fair opportunity to receive a cadaveric organ, HCC-specific scores predicted by our model could be added to MELD scores of patients with HCC.