What is a hemibody?

What is a Hemibody?

A hemibody refers to half of the body, typically used in radiation oncology to describe a radiation treatment technique that targets either the upper or lower half of the body in a single fraction for widespread metastatic disease, particularly for pain relief in multiple myeloma and other cancers with extensive bone metastases. 1

Types of Hemibody Irradiation

Hemibody irradiation (HBI) is categorized based on the anatomical region targeted:

• Upper hemibody irradiation (UHBI): Treats the area from the top of the head to the bottom of the ribs/diaphragm
• Lower hemibody irradiation (LHBI): Treats the area from the bottom of the ribs/diaphragm to the feet
• Middle hemibody irradiation: Less common variant that targets the mid-section of the body 2

Clinical Applications

Hemibody irradiation is primarily used for:

1. Multiple myeloma: Particularly for patients who have:

   • Relapsed after conventional chemotherapy
   • Developed resistance to first-line treatments
   • Widespread painful bone lesions 3, 4

2. Metastatic bone disease: For patients with multiple painful bone metastases, where localized radiation would require too many separate fields 2

Dosing and Administration

• Typical single-fraction doses:

  • Lower hemibody: 7.5-10 Gy
  • Upper hemibody: 6-7.5 Gy (lower dose due to greater sensitivity of thoracic organs) 3

• Double hemibody irradiation (DHBI): Sequential treatment of both upper and lower halves of the body, typically with a 4-6 week interval between treatments to allow for bone marrow recovery 4

Clinical Outcomes

Hemibody irradiation provides:

• Pain relief: 90-95% of patients experience significant reduction in bone pain
• Reduced analgesic requirements: Up to 25% of patients may discontinue opioid analgesics completely
• Quality of life improvement: Significant improvements in functional scales and global health status 2

Side Effects and Considerations

• Hematologic toxicity: Common side effects include thrombocytopenia and neutropenia due to bone marrow suppression
• Gastrointestinal effects: Nausea, vomiting, and diarrhea may occur, particularly with lower hemibody treatment
• Pulmonary effects: Pneumonitis is a concern with upper hemibody treatment
• Sequential timing: When both halves need treatment, adequate recovery time between treatments is essential 3, 4

Other Medical Contexts

The term "hemibody" may also appear in other medical contexts:

• Neurological disorders: "Hemibody tremor" refers to tremor affecting one side (half) of the body, often related to stroke or other central nervous system lesions 5

• Anatomical reference: In general medical terminology, "hemibody" may simply refer to one lateral half of the body (right or left)

It's important to note that while hemibody irradiation was more common in the past, advances in systemic therapies for multiple myeloma and metastatic disease have reduced its frequency of use, though it remains an important palliative option for selected patients with widespread, painful bone metastases.