Saturday, July 13, 202410:30 AM - 11:30 AMPPP01 Presentation Time: 10:30 AM

Purpose

gMCO generated plans for HDR prostate brachytherapy have been shown to be superior to standard reference clinical plans in a blinded pairwise comparison[1]. The purpose of this work, a first-in-man trial, was to compare gMCO and reference plans in terms of planning time and plan quality for prostate HDR brachytherapy 15Gy boosts in a randomized clinical trial.

Materials and Methods

The brachytherapy procedure was as follows: 1) Patient walk-in/installation/anaesthesia 2) Positioning/Catheter implantation under transrectal ultrasound (US) guidance 3) 3D US scan 4) Contouring/catheter reconstruction on Oncentra Prostate (Elekta, Veenendaal, Netherlands) 5) Planning 6) Treatment. Planning (step 5) was performed, after randomization, using either IPSA (Oncentra Prostate, Veenendaal, Netherlands) or gMCO (in-house platform). For gMCO planning, the contours and reconstructed catheters were exported to gMCO at step 4) and the resulting plan was imported on OCP at step 6). The planning times on IPSA or gMCO were recorded. Patients previously had a planning MR in order to identify the gross tumor volume (GTV, PIRADS 3 and above)and, if present, received a boost of 125% of the prescription dose. At the time of writing, 55 (of 60) patients have been accrued and treated on this trial. Of those, only 10 patients had no GTV. Dosimetric parameters (Prostate V100, V150, V200, GTV D90, Urethra D10, Rectum and Bladder V75 and D1cc) of gMCO and IPSA plans were compared (Student's T test) to determine if plan quality and planning times were statistically different.

Results

Figure 1 shows a) a boxplot of the the planning times (minutes), b) a boxplot of the GTV D90 coverage (Gy) and c) a histogram of the proportion of GTVs with more than 19, 19.5 and 20 Gy D90 coverage for gMCO and IPSA for the 55 accrued patients (29 gMCO and 26 IPSA). Figure 1 a) shows that the median planning time for clinical cases is roughly halved (p=0.0002) for gMCO (5.0 min) compared to IPSA (10.0 min) and b) shows a trend towards higher GTV D90s for gMCO planning compared to IPSA (p=0.26). The median GTV volume and standard deviation was 3.5 cc (4.2 cc std) for gMCO and 2.8 cc (2.3 cc std) for IPSA patients (p=0.21). Additionally, we found no learning curve effect in the planning using gMCO. No statistically significant differences were found between dosimetric parameters for the prostate V100, V150, D90, Bladder V75, Rectum V75 and Urethra D10. The prostate V200 was statistically higher for gMCO (p=0.048), possibly because of higher GTV D90 to the (19.8 Gy) compared to IPSA (19.3 Gy). Figure 1c) shows that a superior GTV D90 coverage can be obtained more consistently for gMCO as compared to IPSA at 19, 19.5 and 20 Gy.

Conclusion

This work presents a first-in-man trial of GPU based multicriteria optimization in prostate HDR brachytherapy. The planning time was halved when using gMCO as compared to IPSA. Better GTV D90s were achieved without compromising the OARs. No learning curve effect was present in gMCO planning. [1] C. Bélanger et al., “Inter-observer evaluation of a GPU-based multicriteria optimization algorithm combined with plan navigation tools for HDR brachytherapy”, Brachytherapy 21 (2022), 551-560.