Simultaneously avoiding the hippocampus and hypothalamic-pituitary axis during whole brain radiotherapy: A planning...

Area of Science:

• Radiation Oncology
• Neuro-oncology
• Medical Physics

Background:

• Whole brain radiotherapy (WBRT) is standard for brain metastases and prophylactic cranial irradiation in small cell lung cancer.
• Neurotoxicity, including cognitive, endocrine, and immune deficits, is a significant complication of WBRT.
• Preserving hippocampal function for cognition and the hypothalamic-pituitary axis for endocrine/immune function is critical.

Purpose of the Study:

• To assess the feasibility of delivering WBRT while simultaneously protecting the hippocampus and hypothalamic-pituitary axis.
• To evaluate dose reduction to critical structures using intensity-modulated radiotherapy (IMRT).

Main Methods:

• Thirteen patients with limited-stage small cell lung cancer were included.
• T1-weighted MRI was used for contouring the hippocampus, hypothalamus, and pituitary gland.
• Two equispaced coplanar IMRT plans were generated: WBRT with hippocampus avoidance (H-A) and WBRT with hippocampus, hypothalamus, and pituitary gland avoidance (H-HP-A).

Main Results:

• Both H-A and H-HP-A plans achieved excellent hippocampus protection (mean doses 9.1 and 9.6 Gy, respectively).
• The H-HP-A plan significantly reduced radiation dose to the hypothalamus (mean 11.06 Gy) and pituitary gland (mean 10.66 Gy).
• Both plans demonstrated comparable and acceptable whole brain target coverage (95.1%) and homogeneity.

Conclusions:

• Equispaced coplanar IMRT enables simultaneous protection of the hippocampus and hypothalamic-pituitary axis during WBRT.
• This technique offers a viable strategy to mitigate neurotoxicity and preserve vital functions in patients receiving WBRT.
• The findings support the integration of advanced IMRT techniques for improved patient outcomes in neuro-oncology settings.