IMRT

Prostate

294

Estimated delivered dose of prostate IMRT treatments

P.M.A. van Haar

bladder

rectum

CTV BV EBV PTV

PZ

cog

293 and bladder are created. The latter effectively reduc around BV to zero towards rectum and bladder. IMR made using PLATO/ITP (Nucletron, Veenendaal, The and were created such that the 66.5 Gy-isodose su 70 Gy) enclosed the PTV and the 72.2 Gy-isodose su 76 Gy) enclosed the EBV as much as possible [17, straints for the organs-at-risk (OARs) during the opti Fig. 1. Schematic sagittal view of volumes taken into account du zation. CTV, clinical target volume (= prostate + vesicles); BV (= prostate); PTV, planning target volume (= CTV + 8 mm; dashed boost volume (= BV + 8 mm, excluding overlap with rectum and PZ, peripheral zone; cog, center of gravity of prostate. 215 patients

Fig. 2. Average dose ( D mean

) and D 99% to CTV, boost volume and peripheral zone for the static, uncorrected and corrected plans, with respect to the prescription dose (PD) and

95% of PD. Box plots show medians, and 25th and 75th percentiles; whiskers are 10th and 90th percentiles; dots represent outliers.

P.M.A. van Haaren et al. / Radiotherapy and Oncology 90 (2009) 291–298 Table 2 Dose parameters for targets and organs-at-risk (OARs) of all static, uncorrected and corrected plans, and changes with respect to the static plans. Data are mean ± SD (range). * p < 0.05 vs. BV and vs. PZ; ! p < 0.05 vs. CTV and vs. BV. Parameter Static Uncorrected Corrected Uncorrected-static Corrected-static Targets CTV D mean (Gy) 74.2 ± 1.2 73.8 ± 1.4 74.0 ± 1.2 " 0.4 ± 0.9 " 0.2 ± 0.4 D 99% (Gy) 69.7 ± 1.4 66.6 ± 5.0 68.8 ± 2.6 " 3.1 ± 4.6 * ( " 25.7 " + 1.5) " 1.0 ± 2.2 * ( " 16.5 " + 1.3) BV D mean (Gy) 75.0 ± 1.2 74.6 ± 1.3 74.8 ± 1.2 " 0.3 ± 0.7 " 0.1 ± 0.3 D 99% (Gy) 70.9 ± 1.6 68.7 ± 4.0 70.5 ± 1.8 " 2.3 ± 3.6 ( " 21.3 " + 2.2) " 0.5 ± 0.9 ( " 5.8 " + 0.9) PZ D mean (Gy) 73.3 ± 1.7 72.2 ± 2.7 73.1 ± 1.7 " 1.2 ± 2.3 ! " 0.2 ± 0.5 D 99% (Gy) 71.2 ± 1.9 69.3 ± 4.3 70.9 ± 2.0 " 1.9 ± 3.8 ( " 20.5 " + 5.3) " 0.3 ± 0.8 ( " 3.8 " + 2.2) OAR Ch nges can be accounted for by cor ection (IGRT) protocols or sufficient margins, when movement is limited <10mm