ESTRO 2024 - Abstract Book

S5096

Physics - Radiomics, functional and biological imaging and outcome prediction

ESTRO 2024

Trial participants took oral pimonidazole 500mg/m2 8-16 hours prior to radical prostatectomy. Patient-specific 3D printed prostate moulds [3] were produced by outlining the prostate on T 2 -weighted (T 2 W) images and used to guide prostate whole organ dissection (Figure 1). For each case, a histological section through the centre of the dominant lesion was selected for GLUT1 staining by a specialist urology histopathologist (DS). The GLUT1 labelling used rabbit monoclonal antibody, clone EPR3915 (Abcam ab115730). Pimonidazole labelling used mouse monoclonal antibody, clone 4.3.11.3 (Hypoxyprobe HPI Mab 1). Scanned histological sections were outlined and analysed with HALO software. Tumour GLUT1 H-scores (0-300) were generated by scoring each tumour cell as 0,1,2 or 3 for absent, low, medium or strong intensity GLUT1 staining respectively, then calculating the ratio of the weighted sum of positive cells to the total number of tumour cells. [4] Whole prostate (WP) and dominant prostatic lesion (DIL) were outlined on T 2 W images from both MR scans by a Clinical Oncologist (MS). A ‘normal prostate’ (NP) volume was created by subtracting DIL from WP. Contours were applied to parametric maps from the quantitative MRI. MR values were reported as mean (+/- standard error). A two sided paired t-test was used to compare MR parameters between NP and DIL.

Results:

To date, MR and GLUT1 data have been analysed in 9 of the 20 patients to be recruited onto the study. GLUT1 tumour H-scores ranged from 95.8 – 194.7. 2/9 patients also had pimonidazole results from adjacent sections. (Figure 2)

For 3 tumours in 2 patients (Figure 2) both pimonidazole and GLUT1 staining was acquired. Qualitatively there was good correspondence between histological markers of hypoxia with strong GLUT1 and pimonidazole staining in both transition zone (TZ) tumours in example 1 and weak staining with both markers in the left peripheral zone (PZ) lesion in example 2.

trans was higher in DIL than NP. (Table 1)

Mean values for MR parameters D and v e were lower in DIL than NP and k

Values for R 2 * as well as oxygen-induced ΔR 1 and ΔR 2 , were acquired for NP and DIL but values were susceptible to prostate movement and a motion correction step was required before further analysis.

Table 1. Comparison of MR Parameters between NP and DIL

Mean for NP

Standard Error

Mean for DIL

Standard Error

p*

Volume(cc)

36.56

3.52

2.74

0.59

-

D (µm 2 /ms)

1.357

0.0338

1.158

0.0424

p < 0.01

k trans (min -1 )

0.0953

0.00621

0.144

0.0167

p = 0.01

v e (fraction)

0.447

0.0507

0.332

0.0367

p = 0.01

*Two-sided paired t-test of NP versus DIL values