S. Koswig et al., A comparison of different three-dimensional treatment planning techniques for localized radiotherapy of prostate cancer, STRAH ONKOL, 175(1), 1999, pp. 10-16
Purpose: Four different three-dimensional planning techniques for localized
radiotherapy of prostate cancer were compared with regard to dose homogene
ity within the target volume and dose to organs at risk, dependent upon tum
or stage.
Patients and Methods: Six patients with stage T1, 7 patients with stage T2
and 4 patients with stage T3 were included in this study. Four different 3D
treatment plans (rotation, 4-field, 5-field and 6-field technique) were ca
lculated for each patient. Dose was calculated with the reference point at
the isocenter (100%). The planning target volume was encompassed within the
95% isodose surface. All the techniques used different shaped portal for e
ach beam. Dose volume histograms were created and compared for the planning
target volume and the organs at risk (33%, 50%, 66% volume level) in all t
echniques.
Results: The 4 different three-dimensional planning techniques revealed no
differences concerning dose homogeneity within the planning target volume.
The dose volume distribution at organs at risk show differences between the
calculated techniques. In our study the best protection for bladder and re
ctum in stage T1 and T2 was achieved by the 6-field technique. A significan
t difference was achieved between B-field and 4-field technique only in the
50% volume of the bladder (p = 0.034), between the 6-field and rotation te
chnique (all volume levels) and between 5-field and rotation technique (all
volume levels). In stage T1, T2 6-field and 4-field technique in 50% (p =
0.033) and 66% (p = 0.011) of the rectum volume. Ln stage T3 a significant
difference was not observed between the 4 techniques. The best protection o
f head of the femur was achieved by the rotation technique.
Conclusion: In the localized radiotherapy of prostate cancer in stage T1 or
T2 the best protection for bladder and rectum was achieved by a 3D-planned
conformal 6-field technique. If the seminal vesicles have been included in
the target volume and in the case of large planning target volume other te
chniques should be taken for a better protection for organs at risk e. g. a
3D-planned 4-field technique box technique.