Catherine Alix-Panabieres, PhD, University Medical Center of Montpellier, Montpellier, France, explains how liquid biopsy is an essential complementary tool to tissue biopsy. A tissue biopsy reveals important information at the beginning of the disease but cannot be performed after some treatments. Alternatively, liquid biopsy can provide essential real-time information about the evolution of a cancer, even after treatment. Moreover, the liquid biopsy can analyse metastatic sites that cannot be easily accessed with a needle. The liquid biopsy blood sample can also provide information about disseminated tumor cells, which may be missed in the tissue biopsy. Dr Alix-Panabieres emphasises that liquid biopsy can assist clinicians in deciding which drug to use and when to switch therapeutic treatments. This interview took place at the American Association for Cancer Research (AACR) Annual Meeting 2022 in New Orleans, LA.