Eine Phase III Studie mit Pembrolizumab oder Placebo als Zusatztherapie in Patienten mit Leberkrebs, die vollständig auf die operative Entfernung oder die lokale Ablation des Tumors angesprochen haben.

Biological: Pembrolizumab;Drug: Placebo

Inclusion Criteria:

- Has a diagnosis of HCC by radiological criteria and/or pathological confirmation.

- Has an eligibility scan (CT of the chest, triphasic CT scan or MRI of the abdomen, and
CT or MRI of the pelvis) confirming complete radiological response =4 weeks after
complete surgical resection or local ablation. Randomization needs to occur within 12
weeks of the date of surgical resection or local ablation.

- Has no radiologic evidence of disease prior to enrollment.

- Has an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 within 7
days prior to Cycle 1, Day 1.

- Has a Child-Pugh class A liver score (5 to 6 points) within 7 days prior to Cycle 1,
Day 1.

- Has alpha fetoprotein (AFP) concentration lower than 400 ng/mL within 28 days prior to
Cycle 1, Day 1.

- Has controlled hepatitis B (Hep B).

- Has recovered adequately from toxicity and/or complications from the local
intervention (surgical resection or local ablation) prior to starting study treatment.

- If female, is not pregnant or breastfeeding, and at least one of the following
conditions applies: 1) Is not a woman of childbearing potential (WOCBP); or 2) Is a
WOCBP and using a contraceptive method that is highly effective or be abstinent from
heterosexual intercourse as their preferred and usual lifestyle (a WOCBP must have a
negative pregnancy test within 72 hours before the first dose of study treatment).

- If undergoing surgical resection, has submitted a tumor tissue sample during
Screening.

- Has adequate organ function.

Exclusion Criteria:

- Has a known additional malignancy that is progressing or has required active
antineoplastic treatment (including hormonal) or surgery within the past 3 years.

- Has had esophageal or gastric variceal bleeding within the last 6 months.

- Has clinically apparent ascites on physical examination.

- Has had clinically diagnosed hepatic encephalopathy in the last 6 months.

- Has received local therapy to liver ablation other than with radiofrequency or
microwave ablation.

- Has a history of (noninfectious) pneumonitis/interstitial lung disease that required
steroids or has current pneumonitis/interstitial lung disease.

- Has an active infection requiring systemic therapy.

- Has dual active Hepatitis B Virus (HBV) and Hepatitis C Virus (HCV) infection at study
entry.

- Has a known history of human immunodeficiency virus (HIV) infection.

- Has known active tuberculosis (TB; Bacillus tuberculosis).

- Has received prior therapy with an anti-PD-1, anti-PD-L1, or anti PD-L2 agent or with
an agent directed to another stimulatory or co-inhibitory T-cell receptor (eg, CTLA-4,
OX-40, CD137).

- Has received prior systemic anti-cancer therapy for HCC including investigational
agents.

- Is receiving any of the following prohibited concomitant therapies:1) Antineoplastic
systemic chemotherapy or biological therapy; 2) Immunotherapy not specified in this
protocol; 3) Investigational agents other than pembrolizumab; 4) Radiation therapy; 5)
Oncological surgical therapy; or systemic glucocorticoids for any purpose other than
to modulate symptoms from an AE that is suspected to have an immunologic etiology.

- Has received a live vaccine within 30 days prior to the first dose of study treatment.

- Is currently participating in or has participated in a study of an investigational
agent or has used an investigational device within 4 weeks prior to Cycle 1, Day 1.

- Has a diagnosis of immunodeficiency or is receiving chronic systemic steroid therapy
or any other form of immunosuppressive therapy within 7 days prior to Cycle 1, Day 1.

- Has severe hypersensitivity (=Grade 3) to pembrolizumab and/or any of its excipients.

- Has an active autoimmune disease that has required systemic treatment in past 2 years.

- Has a known psychiatric or substance abuse disorder that would interfere with the
participant's ability to cooperate with the requirements of the study.

- Has had an allogenic tissue/solid organ transplant.