ESTRO 2024 - Abstract Book

S2381

Clinical - Urology

ESTRO 2024

DIL volumes on MRI and PET showed strong agreement (Spearman correlation coefficient 0.871; p<0.001) (Figure 2a) with a statistically non-significant increment contributed by PSMA-PET (p=0.34). The difference between GTVunion and GTVoverlap, however, was statistically significant (p<0.001) (Figure 1) . The median PSMA-PET %SUVmax auto-contouring threshold corresponding with DIL-MRI was 50% (IQR, 40%-58%). DSC and JI between DIL PET and DIL-MRI were 0.59 (IQR, 0.42-0.71) and 0.41 (IQR, 0.24-0.53), respectively. There was strong negative correlation between baseline DIL SUVmax and %SUVmax (DILx%) selected as DIL-PET (Spearman correlation coefficient -0.788, p<0.001) (Figure 2b) . No significant correlation was seen between DIL-MRI volume, either, with %PSMA SUVmax auto-contouring threshold, or, with concordance metrics (DSC and JI).

The median of the dose received by 98% (D98) of CTV prostate , GTV union and GTV overlap were 35.73 Gy (IQR, 35.60-35.92), 39.70 Gy (IQR 39.18-39.88) and 41.90 Gy (IQR 41.78-42.15) respectively. The rectum and bladder received a median of 35.50Gy and 36.23 Gy, respectively, to 1 cc (D1cc). Median maximum point dose (Dmax) to the urethra was 39.31 Gy (IQR, 38.83-39.47).