See All 1 What Is Radiation Therapy? 2 How Does Radiation Therapy Work? 3 When Is Radiation Therapy Used? 4 What Happens If I Need Radiation Therapy? 5 What Happens During External Radiation Treatment? 6 How Long Does The Radiation Treatment Take? 7 When Is Internal Radiation Therapy Used? 8 Radiation Therapy: What Are The Side Effects Of Treatment? 9 Radiation Therapy: Frequently Asked Questions 10 Radiation Therapy: Putting It All Together 11 Radiation Therapy: Glossary 12 Radiation Therapy: Additional Sources Of Information