AUTHOR=Varga Linda , Besenyi Zsuzsanna , Paczona Viktor R. , Farkas István , Urbán Szabolcs , Sipka Gábor , Pávics László , Varga Zoltan , Fodor Emese , Hideghéty Katalin , Olah Judit , Bajory Zoltán , Maráz Anikó 

TITLE=Prostate-specific membrane antigen-based imaging for stereotactic irradiation of low-volume progressive prostate cancer: a single-center experience

JOURNAL=Frontiers in Oncology

VOLUME=Volume 13 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2023.1166665

DOI=10.3389/fonc.2023.1166665

ISSN=2234-943X

ABSTRACT=Introduction: Prostate-specific membrane antigen (PSMA) is a transmembrane protein that may be expressed on the surface of prostate cancer (PC) cells. It enables a more sensitive and specific diagnosis PC, compared to conventional anatomical imaging.The integration of PSMA-based imaging in the personalized radiotherapy of PC patients and the evaluation of its impact on target volume definition if stereotactic body radiotherapy (SBRT) is planned for locally recurrent or oligometastatic disease.The data of 363 examinations were analyzed retrospectively. Inclusion criteria were histologically verified PC and clinical data suggesting local recurrence or distant metastasis. Whole body 99m Tc-PSMA-I&S SPECT/CT or 18 F-JK-PSMA-7 PET/CT was carried out, the evaluation of the scans and biological tumor volume contouring was done at the Department of Nuclear Medicine. The target volume delineation on topometric CT (TCT) scan was performed at the Department of Oncotherapy. The comparison of the two volumes was performed by image fusion and registration.Results: From 363 PSMA isotope-based examinations, 84 lesions of 64 patients were treated with SBRT. In 50 patients 70 lesions were examined for intermodality comparison. Target volume defined by the PSMA density was significantly smaller than tumor size defined by the TCT scan: GTVCT (gross tumor volume on the TCT): 27.58 ± 46.07 cm 3 , BTVPSMA (biological target volume on the PSMA-based examination): 16.14 ± 29.87 cm 3 . During geometrical analyses the dice similarity coefficient (DSC) was 0.56 ± 0.20 (0.07 -0.85). PSA control was performed to evaluate the response: mean pre-RT PSA was 16.98 ng/ml (±SD: 33.81), post-RT PSA at 3 months after SBRT was 11.19 ng/ml (±SD: 32.85). 3 months posttherapy PSMA-based imaging was performed in 14 cases, in which we observed a decrease or cessation of isotope uptake. Conventional imaging control was performed in 42 cases (65.6% of all cases): 22 (52.4%) complete remissions, 14 (33.3%) partial remissions, 4 (9.5%) stable diseases, and 2 (4.8%) progressive diseases were described.PSMA-based imaging is a promising diagnostic method for specifying the stage and detecting the low volume progression. Our results suggest that PSMA-based hybrid imaging can influence treatment decision and target volume delineation for SBRT.