Klinisk strålebiologi - normalvev

Tidlig reaksjon

teleangiectasi

Sen reaksjon

Basis for dose-respons-kurver

Stigetallet for dose-responskurven

Gaussian distribution of radiation sensitivity

Dose response curve

Uniquely described by two parameters: - gradient at 50% response

levelD50% - dose to achieve 50%

response

Gaussian distribution of technical and dosimetrical

factors

biolo > clin Pettersen M et al Radiotherapy and Oncology 2008

Clinical dose response curve

Uniquely described by two parameters: - gradient at 50% response

levelD50% - dose to achieve 50%

response

is linked to the standard deviation, , of the Gaussian distribution by:

21

Pettersen M et al Radiotherapy and Oncology 2008

22bioldoseclin ),( bioldoseclin f and ),( bioldoseclin f

Steepness of clinical dose-response curve is depending of the dose variation

Pettersen M et al Radiotherapy and Oncology 2008

Roué et al 2004ESTRO-Equal external audit102 centres, 235 beams in France3% beams had deviations > 5%24 centres had deviations > 5%

Design of a randomised clinical study

• The null hypothesis is that the two treatment options produce no different outcome

• To prove a difference, the null hypothesis has to be rejected

• The number of patients needed is linked to , the difference in response (R), the level of significance () and the power ()

= 0.2 = 0.05

Pettersen M et al Radiotherapy and Oncology 2008

The number of patients required

Conclusions:To keep the number of patients

required for RCT as low as possible, the standard deviation of the

dosimetry should be kept below 5%.

Volumeffet for rektumblødning

Strandqvist plot

-kill

-kill

LQ-formelverket