This study focuses on patients who are about to begin treatment for advanced liver cancer at Cedars-Sinai. The purpose of the study is to determine how bacteria in the digestive tract could contribute to response to liver cancer treatment. The bacteria in the digestive tract help maintain a healthy immune system and may therefore affect how the body responds to treatments that target the immune system. Researchers will evaluate data in participants’ medical records; oral and stool samples will be collected to characterize bacteria in the digestive tract. The study aims to determine whether a biomarker test is helpful in predicting a patient’s response to liver cancer treatment. A biomarker is a biological molecule found in blood, other body fluids, or tissues that may be a sign of a condition or disease.