Hypofractionation [Neurosurgery Wiki]

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====== Hypofractionation ======

**Definition:**  
''Hypofractionation'' refers to a radiotherapy regimen in which **fewer but larger doses (fractions)** of radiation are delivered compared to conventional schedules. The total dose may be similar or slightly lower, but the treatment is completed in fewer sessions.

===== 🔬 Radiobiological Basis =====
Tumors with a **low α/β ratio** (e.g., prostate cancer, some slow-growing brain tumors like meningiomas) are **more sensitive to higher doses per fraction** and may benefit from hypofractionated regimens.

> ⬇️ Low α/β → Better suited for hypofractionation  
> ⬆️ High α/β → Prefer conventional fractionation

===== ⚙️ Technical Requirements =====
  * **Precise image guidance (IGRT)**
  * **Accurate immobilization**
  * **Advanced treatment planning systems**
  * Often uses **IMRT** or **SBRT** platforms

===== 🧠 Applications in Neurosurgery =====
  * **Meningiomas** (especially skull base)
  * **Brain metastases** (as alternative to single-fraction radiosurgery)
  * **Chordomas and spinal lesions**
  * Selected cases of **gliomas** and **post-op irradiation**

> Hypofractionation offers **outpatient treatment**, reduced patient burden, and potential cost savings — when properly indicated.

===== ⚠️ Limitations =====
  * Risk of **late toxicity** in surrounding critical structures (optic pathways, brainstem)
  * Not suitable for **rapidly proliferating tumors**
  * Requires **high infrastructure and QA standards**

===== 📚 Related Terms =====
  * [[ultra_hypofractionation]]
  * [[stereotactic_body_radiotherapy]]
  * [[alpha_beta_ratio]]
  * [[radiobiology]]
  * [[fractionation_schedule]]