Photon-counting computed tomography (PCCT) marks a significant advancement over conventional Energy-integrating detector CT systems. This review highlights PCCT's superior spatial and contrast resolution, reduced radiation dose, and multi-energy imaging capabilities, which address key challenges in radiotherapy, such as accurate tumor delineation, precise dose calculation, and treatment response monitoring. PCCT's improved anatomical clarity enhances tumor targeting while minimizing damage to surrounding healthy tissues. Additionally, Metal artifact reduction and quantitative imaging capabilities optimize workflows, enabling ART and radiomics-driven personalized treatment. Emerging clinical applications in brachytherapy and radiopharmaceutical therapy show promising outcomes, although challenges like high costs and limited software integration remain. With advancements in artificial intelligence and dedicated radiotherapy packages, PCCT is poised to transform precision, safety, and efficacy in cancer radiotherapy, marking it as a pivotal technology for future clinical practice.