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68Ga-PSMA-PET/CT Imaging of Localized Prostate Cancer Patients for IMRT

W Laub

W Laub1*, L Thomas2 , A Hung1 , C Thomas1 , M Essler2 , R Bundschuh2 , (1) Oregon Health & Science Univ, Portland, OR, (2) University Hospital Bonn, Bonn


WE-RAM3-GePD-J(A)-2 (Wednesday, August 2, 2017) 10:30 AM - 11:00 AM Room: Joint Imaging-Therapy ePoster Lounge - A

Purpose: The purpose of our study was to show the potential benefits of using 68Ga-PSMA-PET/CT imaging for integrated boost or boost only treatment planning of prostate cancer patients. The potential gain of such an approach is the improvement of tumour control and reduction of the dose to organs-at-risk at the same time.

Methods: 21 prostate cancer patients (70yrs average) without previous local therapy received 68Ga-PSMA-PET/CT imaging. Organs-at-risk and standard prostate target volumes were manually defined on the obtained datasets. A PET active volume GTV_PET was segmented with a 40% of the maximum activity uptake in the lesion as threshold. Five different treatment plan variations were calculated for each patient. Analysis of derived treatment plans was done according to QUANTEC with in-house developed software. Tumor Control Probability (TCP) and Normal Tissue Complication Probability (NTCP) was calculated for all plan variations.

Results: Comparing the conventional plans to the plans with integrated boost and plans just treating the PET-positive tumor volume, we found that TCP increased to (95.2  0.5)% for an integrated boost with 75.6 Gy, (98.1  0.3)% for an integrated boost with 80 Gy, (94.7  0.8)% for treatment of PET-positive volume with 75 Gy, and to (99.4  0.1)% for treating PET-positive volume with 95 Gy (all p < 0.0001). For the integrated boost with 80 Gy a significant increase of the median NTCP of the rectum was found, for all other plans no statistical significant increase in the NTCP neither of the rectum nor the bladder was found.

Conclusion: Our study demonstrates that the use of 68Ga-PSMA-PET/CT image information allows for more individualized prostate treatment planning and better targeting of active tumour volumes. TCP values of identified active tumor volumes were increased, while rectum and bladder NTCP values either remained the same or were even lower.

Funding Support, Disclosures, and Conflict of Interest: This project was funded in part by the Deutsche Forschungsgemeinschaft (BU 3395/1-1).

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