Retreatment (Reirradiation)

  • Patients may relapse locally or develop a second tumor.

  • Principle: calculate cumulative BED/EQD2, consider tissue recovery over time.

  • CNS and spinal cord are most limiting → very low retreatment tolerance.

Adaptive Radiotherapy

  • Definition: modifying the treatment plan based on anatomical or biological changes during therapy.

  • Examples:

    • Tumor shrinkage → reduce margins.

    • Daily cone-beam CT/MRI → recontour.

  • Biological adaptivity: dose painting based on hypoxia PET, genomics, or radiosensitivity.

Clinical relevance

  • Improves therapeutic ratio by personalizing treatment.

  • Still evolving: MR-Linac, radiogenomic approaches.

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