<p>This work presents a leaky waveguide-based biosensor design for detecting various types of cancer cells at an early stage. The sensor operates by detecting changes in light properties resulting from variations in the refractive index occurring on or near the sensor surface for normal and suspicious cells. The proposed TeO₂ waveguide sensor features a trench on both sides of a central core on the SiO₂ substrate that enables propagating modes to become leaky. The parameters of the waveguide sensor are optimized to achieve a significant confinement loss for a specific wavelength. The finite element method is utilized to compute the leakage loss of the modes, and sensitivity is calculated for six different types of cancer cells, such as breast cancer, blood cancer, adrenal gland cancer, skin cancer, and cervical cancer. For biosensing applications, the maximum sensitivity was found to be around 26 dB/m/RIU with a minimum detection limit of 11.50&#xa0;nm RIU per unit loss for skin cancer (basal). Such design of an on-chip leaky waveguide-based biosensor will open up new possibilities for the detection and diagnosis of different types of cancer cells.</p>