Metastatic disease occurs when cancer cells spread from their original site to other parts of the body. This process can happen through the bloodstream or lymphatic system, allowing the cancer to form new tumors in organs such as the lungs, liver, or bones. Once cancer has metastasized, it is often more challenging to treat than localized cancer. Treatment options may include chemotherapy, radiation therapy, or targeted therapies, depending on the type of cancer and its location. Early detection and intervention are crucial for improving outcomes in patients with metastatic disease.