Clinical application of TCP・NTCP

Lyman JT. Complication probability as assessed from dosevolume histograms. Radiat Res Suppl 1985; 8:S13–S19.

Because of the large amount of data generated by 3D treatment planning, new tools are being developed for the evaluation and optimization of the plans. Estimates of the probability of local control of the tumor and for the probability of specific normal tissue complications are among the new tools. The normal tissue complication probability (NTCP) is based on clinical estimates of the tolerance doses for specific tissues/organs. These tolerance doses are assumed to apply for uniform partial and full volume irradiations delivered at 2 Gy per fraction and 5 fractions per week. A different tolerance dose may apply when the dose is delivered at a different dose per fraction and over a different period of time. This study evaluates the maximum change expected in the NTCP when the normal structure receives the dose at a different dose per fraction than the target volume due to different choices in the delivery of the daily fraction.

TCP & NTCP

Delivered dose

TCP

NTCP

TC

P o

r N

TC

P(%

)

100

75

50

25

Usefulness of TCP

Detection for the cold point in DVH

Cold point

Low

Usefulness of TCP and NTCP

Comparison of treatment plans

CFIMRT

IMRT

Usefulness of TCP and NTCP

Refine treatment plans

TCP 32.28 TCP 26.83NTCP 61.30% NTCP 14.91%