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Fatourou et al. Hepatoma Res 2018;4:63 I http://dx.doi.org/10.20517/2394-5079.2018.62 Page 7 of 11

Table 4. The RETREAT score for the prediction of HCC recurrence
RETREAT score
Predictor Retreat points
AFP at LT, ng/mL
0-20 0
21-99 1
100-999 2
≥ 1000 3
Microvascular invasion 2
Largest viable tumour diameter (cm) plus No of viable tumours*
0 0
1.1-4.9 1
5-9.9 2
≥ 10 3
*The score is calculated by adding the individual points for each variable. The score is zero (0) if no viable tumour identified. AFP: alpha-
fetoprotein; HCC: hepatocellular carcinoma; LT: liver transplantation

RETREAT score
The Risk Estimation of Tumour Recurrence after Transplant (RETREAT) score which consists of the sum of
the largest viable tumour diameter and number of viable tumours on explant, microvascular invasion and AFP
at the time of LT, was developed in a cohort of 721 patients across 3 U.S centres and externally validated in a
cohort of 340 patients from a single centre in Canada. The RETREAT score is calculated as shown in Table 4.
Patients with a RETREAT score of 0 have a predicting 1 and 5 year recurrence risk of 1% (95% CI : 0.0%-2.1%)
and 2.9% (95% CI : 0.0%-5.6%) respectively which can increase to 29.3% (95% CI : 25.5%-50.5%) and 75.2% (95%
CI : 56.7%-85.8%) in patients with a RETREAT score of 5 or higher. One of the advantages of the RETREAT
score over other proposed scoring systems is that it takes into consideration the effect of pre-transplant
locoregional treatment by including only viable tumours into the model equation. Although this score can only
be calculated post LT, it can be utilised to determine surveillance strategies, as well as influence decisions on
immunosuppression regimens and adjuvant therapies post LT.

In a study by Mehta et al. , the RETREAT score was validated by using the United Network for Organ
[13]
Sharing database in 3275 patients transplanted for HCC, between 2012 and 2014. Based on explant findings, the
RETREAT score discriminated well between patients with low and high risk and recurrence and higher scores
were associated with poor survival outcomes. Specifically, patients with a RETREAT score of 0 had a 3 year
recurrence and survival rate of 1.6% and 91% respectively, whereas, for patients with a RETREAT score of 5 or
higher, the 3 year recurrence and survival rates were 29% and 58% accordingly. The RETREAT score was also
shown to be superior to Milan criteria on explant, in predicting HCC recurrence. Finally, the RETREAT score
was associated with a shorter time to HCC recurrence with a median time to recurrence of 10.9 months (IQR
51, -17.9) in patients with a score ≥ 4 .
[13]

HALT HCC score
The Hazzard associated with Liver Transplantation for Hepatocellular Carcinoma (HALT-HCC) score was
developed based on retrospective data from 420 patients transplanted for HCC in a single US centre, and
included MELD-sodium (MELD-Na), tumour burden score (tumour maximum diameter plus number of
lesions) and AFP as shown in the following equation; HALT-HCC = (1.27 × tumour burden score) + (1.85 ×
[29]
lnAFP) + (0.26 × MELD-Na) . The HALT-HCC score was externally validated in 13,717 patients that derived
from the SRTR and was significantly associated with overall survival (HR 1.06%, 95% CI : 1.05-1.07). Patients
were shown to have similar risk of death when stratified by the HALT HCC score, regardless of being within
or beyond the Milan criteria prior to transplantation. The advantage of the HALT-HCC score over the other
published scores is that it takes into consideration not only the tumour burden and the biological behaviour,
[29]
but also the underlying liver function at the time of LT .