Tumor Control Probability (TCP)

• Probability of eradicating all clonogenic tumor cells with a given dose.

• Modeled mathematically using Poisson statistics.

• Depends on:

  • Initial number of clonogens

  • Radiosensitivity

  • Dose distribution

  • Microenvironment (oxygenation, repair).

Normal Tissue Complication Probability (NTCP)

• Probability that a normal tissue develops a clinically relevant complication.

• Based on:

  • Total dose

  • Dose per fraction

  • Irradiated volume

  • Organ-specific sensitivity.

Therapeutic Ratio

• Ideal treatment → maximize TCP while minimizing NTCP.

• Balancing act of modern radiotherapy.