*Purpose: The Risk Estimation of Tumor REcurrence After Transplant (RETREAT) score includes 3 variables that independently predict HCC recurrence: microvascular invasion (MVI), AFP at liver transplant (LT), and the sum of the largest viable tumor diameter and number of viable tumors on explant. No prospective multicenter study has validated RETREAT in a contemporary cohort of HCC patients.
*Methods: We are conducting an ongoing prospective multicenter study enrolling consecutive HCC patients who underwent LT after January 2018 at 7 sites in the U.S. We used a C-statistic to assess RETREAT risk stratification accuracy for post-LT HCC recurrence and Kaplan-Meier analysis to estimate recurrence free survival (RFS) and overall survival (OS).
*Results: Our cohort (n=660) had a median age at LT of 64 (IQR 59, 68); Hep C (41%) and NASH (17%) as common underlying etiologies; and a median time from HCC diagnosis to transplant of 17 months (11, 25). Most received locoregional therapy (LRT) prior to transplant (91%) and had an AFP ≤20 ng/ml at transplant (83%). On explant pathology, 21% had MVI, 26% had complete tumor necrosis, and 20% were beyond Milan criteria. RETREAT scores were distributed as follows: 0 (26%), 1-2 (48%), 3-4 (19%), and 5+ (7%). Median post-transplant follow-up time was 2.5 years (1.4, 3.7). Recurrence rate was 7.3% with a median time to recurrence of 11 months (5,20) and most cases detected by surveillance imaging (81%). RETREAT had a C-statistic of 0.81 for recurrence prediction. Post-LT 3-year RFS decreased with increasing RETREAT Score: 100% for RETREAT 0, 95% for RETREAT 1-2, 80% for RETREAT 3-4, and 60% for RETREAT 5+. Similarly, post-LT 3-year OS decreased with increasing RETREAT Score: 92% for RETREAT 0, 93% for RETREAT 1-2, 84% for RETREAT 3-4, and 66% for RETREAT 5+. Among the 48 patients with post-transplant HCC recurrence, post-recurrence OS was worse if recurrence was not initially detected by surveillance imaging (p = 0.03).
*Conclusions: RETREAT remains a strong prognostic score for post-LT HCC recurrence in this contemporary cohort of U.S. patients undergoing LT. Our results support RETREAT-based surveillance strategies, including no surveillance in patients with RETREAT score of 0 and more intensive surveillance with possible novel adjuvant therapies in those with RETREAT score of 5+.

Jonathan Li

UCSF

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