Introduction: There are no standard systemic therapies for the treatment of fibrolamellar carcinoma (FLC), as surgery remains the only definitive option. We share our experiences using systemic “triple therapy” (TT) with 5-fluorouracil, interferon, and nivolumab for the treatment of relapsed, refractory, metastatic, or unresectable FLC. Methods: Data from all patients who received TT from May 2018 to July 2020 were reviewed to assess response, survival, and toxicity. Results: A total of 22 patients were treated with TT, of which 14 (median age of 21 years) were evaluable. They received a median of 18 cycles (8–44). At the time of analysis, the median progression-free survival was 9 months (4.5–26), 29% longer than prior to TT, with 5 patients achieving clinical remission, 8 patients stable or improving, and 1 progression. Overall objective response (clinical remission + partial response) was 50% and tumor control rate (clinical remission + partial response + stable disease) was 93%. Two patients withdrew from treatment due to side effects. Discussion/Conclusion: Our early results support TT as a promising medical option to slow disease progression and prolong survival in high-risk patients with FLC. TT can be administered in the outpatient setting and has shown good tolerability. Further longitudinal data is needed to confirm outcomes, especially in patients still early in their treatment.

e16161 Background: Fibrolamellar carcinoma (FLC) is an exceedingly rare liver cancer affecting children and young adults without underlying liver disease. Complete surgical resection is the primary treatment option, but recurrence is common. There are currently no established systemic therapies. We have treated patients in both the neoadjuvant and adjuvant setting with three novel combination therapies: 5-fluorouracil/interferon/nivolumab (“Triple Therapy” or TT), gemcitabine/oxaliplatin/lenvatinib (GOL), and nivolumab/lenvatinib/quercetin (NLQ). The purpose of this study was to evaluate objective responses and tolerability of three multi-agent systemic therapies in the treatment of FLC. Methods: Data from all patients with FLC who received TT, GOL, or NLQ between May 2018 and February 2021 were reviewed. Patients who received a minimum of six cycles of systemic therapy with follow up scans at least two months after initiation were assessed based on objective response, survival, and toxicity. Results: Twenty-nine patients with FLC who were treated with novel multi-agent systemic therapy were evaluable based on the above criteria. Median age at start of treatment was 20 (7-52; 16F, 12M, 1 non-disclosed). Twenty-three patients received one combination therapy (13 TT, 8 GOL, 2 NLQ), five received two different lines (3 TT/NLQ, 2 TT/GOL), and one patient received all three novel combinations. Between our 29 patients, they had relapsed 36 total times, and 11 had already tried 2+ systemic therapies. Best RECIST 1.1 objective response (clinical remission + partial response) and tumor control rate (clinical remission + partial response + stable disease) were 58%/95%, 55%/100%, and 33%/83% for TT, GOL, and NLQ respectively. The median longest Progression Free Survival (PFS) on any novel multi-agent regimen was 9 months (2-29; 9.5 for TT, 7 for GOL, 6.5 for NLQ), with 18 patients still receiving the therapy extending their PFS. Of those with previous relapses, 56% have a PFS longer than their previous longest remission and 69% have a PFS longer than their previous shortest time to relapse. Half of patients with previous relapses are still receiving the treatment responsible for their longest PFS. Fever, chills, and nausea were the most common adverse effects experienced throughout all three regimens. Seven patients experienced 1+ grade 3 adverse event. There were no toxic deaths or organ failure. Two patients died as a result of disease; their longest PFS (1 on GOL, 1 on TT) were nine and 10 months. Conclusions: FLC is a devastating cancer with patients often relapsing even after successful surgical remission. There is a strong need for effective and tolerable systemic therapies for those with unresectable, relapsed, progressive, or metastatic disease. We have had promising results in treating FLC and prolonging survival with minimal toxicities using novel multi-agent regimens.