What role does chemotherapy play in cancer treatment?

Chemotherapy plays a crucial role in cancer treatment primarily by targeting and killing rapidly dividing cells, which includes cancer cells. This treatment modality is effective because cancer cells typically divide more rapidly than most normal cells. However, it is important to note that chemotherapy is not selective and can also affect healthy cells that divide quickly, such as those found in the bone marrow, gastrointestinal tract, and hair follicles. This non-specific action is what leads to common side effects, such as hair loss, nausea, and an increased risk of infection, as these healthy cells are also impacted.

The other options do not accurately reflect the primary role of chemotherapy in cancer treatment. While chemotherapy may have ancillary effects, such as enhancing the effectiveness of radiation in some contexts, it is primarily recognized for its direct action on rapidly dividing cells. It does not primarily strengthen the immune system or selectively target only healthy cells, which would indeed reduce side effects but is not a characteristic of chemotherapy. Thus, the emphasis on its role in killing rapidly dividing cells encapsulates its main function in cancer therapy.