The client is diagnosed with a metastatic brain tumor, and radiation therapy is scheduled. The client asks the nurse, “Why not try chemotherapy first? It has helped my other tumors.” The nurse’s...

The client is diagnosed with a metastatic brain tumor, and radiation therapy is scheduled. The client asks the nurse, “Why not try chemotherapy first? It has helped my other tumors.” The nurse’s response is based on which scientific rationale?

1. Chemotherapy is only used as a last resort in caring for clients with brain tumors.

2. The blood–brain barrier prevents medications from reaching the brain.

3. Radiation therapy will have fewer side effects than chemotherapy.

4. Metastatic tumors become resistant to chemotherapy and it becomes useless.