Spatiotemporal radiotherapy planning using a global optimization approach.

Area of Science:

• Radiation oncology
• Medical physics
• Computational biology

Background:

• Fractionated radiotherapy delivers radiation in multiple sessions.
• Optimizing dose distribution is crucial for maximizing tumor control and minimizing side effects.
• Current methods often use time-invariant dose distributions.

Purpose of the Study:

• To quantify the therapeutic gain achievable by altering radiation dose distribution over treatment sessions.
• To develop and evaluate a spatiotemporally integrated planning approach for radiotherapy.
• To compare the clinical quality of heterogeneous vs. homogeneous dose distributions using equivalent uniform BED (EUBED).

Main Methods:

• Developed a spatiotemporally integrated planning approach optimizing spatial and temporal dose modulations simultaneously.
• Utilized equivalent uniform BED (EUBED) to assess dose distributions.
• Solved the large-scale non-convex optimization problem using global optimization techniques.
• Tested the approach on stylized cancer cases and performed sensitivity analyses.

Main Results:

• Spatiotemporal plans achieved a larger biologically effective dose (BED) in the target volume compared to conventional plans.
• This therapeutic gain was realized without increasing BED in critical structures.
• The benefit arises from irradiating different tumor regions across sessions.
• Quantified the trade-off between therapeutic gain and the number of distinct dose distributions.

Conclusions:

• Spatiotemporal radiotherapy planning offers a potential method to enhance therapeutic outcomes.
• This approach allows for greater biological effect in tumors while sparing organs at risk.
• The number of distinct dose distributions influences therapeutic gain, with diminishing returns.