What does metastasis refer to in the context of cancer?

Metastasis refers specifically to the process by which cancer cells spread from the primary tumor to other parts of the body. This occurs when cancer cells break away from the original (primary) tumor, travel through the lymphatic system or bloodstream, and establish new tumors (secondary tumors) in other organs or tissues. This characteristic of cancer is significant because it impacts the disease's progression and treatment options. Understanding metastasis is crucial for determining the stage of cancer and the appropriate interventions, as it usually indicates a more advanced stage of the disease.

The other options do not accurately define metastasis, as they focus on different aspects of cancer or its treatment rather than the spread of the disease itself. The initial growth of a tumor describes the formation of cancer, localized destruction of tissue refers to the impact of a tumor on its immediate environment, and treatment involves various methods to combat cancer rather than defining how it spreads.