A complementary cell analysis method has been developed to assess the dynamic interactions of tumor cells with resident tissue and immune cells using optical light scattering and impedance sensing to shed light on tumor cell behavior. The combination of electroanalytical and optical biosensing technologies integrated in a lab-on-a-chip allows for continuous, label-free, and noninvasive probing of dynamic cell-to-cell interactions between adherent and nonadherent cocultures, thus providing real-time insights into tumor cell responses under physiologically relevant conditions. While the study of adherent cocultures is important for the understanding and suppression of metastatic invasion, the analysis of tumor cell interactions with nonadherent immune cells plays a vital role in cancer immunotherapy research. For the first time, the direct cell-to-cell interactions of tumor cells with bead-activated primary T cells were continuously assessed using an effector cell to target a cell ratio of 10:1.