Dose-escalation using intensity-modulated radiotherapy for prostate cancer – Evaluation of the dose distribution with and without 18F-choline PET-CT detected simultaneous integrated boost
Received 12 March 2009; received in revised form 24 July 2009; accepted 25 July 2009. published online 01 September 2009.
Abstract
Background and purpose
The aim of the study was to evaluate the impact of a dose escalation to an 18F-choline PET-CT defined simultaneous integrated boost (IB) on the dose distribution and changes of the equivalent uniform dose (EUD).
Materials and methods
PET-CT was performed in 12 consecutive patients for treatment planning. An intraprostatic lesion was defined by a tumour-to-background uptake value ratio >2 (GTVPET). Dose escalation was focused only on the intraprostatic lesion. Two comparisons were evaluated: whole prostate irradiation to 76Gy±boost to 80Gy (C1) and whole prostate irradiation to 66.6Gy±boost to 83.25Gy (C2).
Results
PTV/GTVPET+margins were covered by a mean EUD of 75.9/76.1Gy vs. 77.1/80.1Gy (C1) and 66.5/66.2Gy vs. 71.1/82.9Gy (C2) (p<0.01, respectively). Concerning the organs at risk, EUD increased slightly with an additional boost (mean EUD for bladder: C1 53.2Gy vs. 53.8Gy; C2 43.0Gy vs. 45.1Gy; for rectum: C1 52.0Gy vs. 52.6Gy; C2 43.0Gy vs. 45.4Gy; p<0.01, respectively). The distance to the organs at risk had a significant impact on the respective maximum doses in the treatment plans with IB.
Conclusions
Treatment planning with IB allows an individually adapted dose escalation. The therapeutic ratio can be improved by a considerable dose escalation to the macroscopic tumour, but only minor EUD changes to the bladder and rectum.
ABSTRACT