Abstract
PurposeAccurate delineation of intraprostatic gross tumor volume (GTV) is mandatory for successful fusion biopsy guidance and focal therapy planning of prostate cancer (PCa). Multiparametric magnetic resonance imaging (mpMRI) is the current gold standard for GTV delineation; however, prostate-specific membrane antigen positron emission tomography (PSMA-PET) is emerging as a promising alternative. This study compares GTV delineation between mpMRI and 68Ga-PSMA-PET in a large number of patients using validated contouring approaches.MethodsOne hundred one patients with biopsy-proven primary PCa who underwent mpMRI and 68Ga-PSMA-PET within 3 months before primary treatment were retrospectively enrolled. Clinical parameters (age, PSA, Gleason score in biopsy) were documented. GTV based on MRI and PET images were delineated; volumes measured and laterality determined. Additionally, biopsy data from 77 patients was analyzed. Univariate and multivariate binary logistic regression analyses were performed using concordance in laterality as the endpoint.ResultsIn total mpMRI and 68Ga-PSMA-PET detected 151 and 159 lesions, respectively. Median GTV-MRI (2.8 ml, 95% CI 2.31–3.38 ml) was significantly (p < 0.0001) smaller than median GTV-PET (4.9 ml, 95% CI 3.9–6.6 ml). 68Ga-PSMA-PET detected significantly more bilateral lesions than mpMRI (71 vs 57, p = 0.03). Analysis of patients with bilateral lesions in biopsy showed a significant higher concordance of laterality in 68Ga-PSMA-PET (p = 0.03). In univariate analysis, PSA level and volume of GTV-MRI had an impact on concordance in laterality (p = 0.02 and p = 0.01), whereas in multivariate analysis, only GTV-MRI volume remained significant (p = 0.04).ConclusionMpMRI and 68Ga-PSMA-PET detect a similar amount of PCa lesions. However, GTV-PET had approximately twice the volume (median 4.9 ml vs 2.8 ml) and detected significantly more bilateral lesions than mpMRI. Thus, 68Ga-PSMA-PET gives highly important complementary information. Since we could not find any strong evidence for parameters to guide when 68Ga-PSMA-PET is dispensable, it should be performed additionally to MRI in patients with intermediate and high-risk PCa according to D’Amico classification to improve GTV delineation.
Highlights
Prostate cancer (PCa) is the most common tumor entity for men in North America [1] and Europe [2], and PCa incidence rates are rising steadily in Asian countries as well [3]
The accurate delineation of intraprostatic tumor burden is mandatory for successful fusion biopsy guidance [4] and for focal therapy planning such as focal dose escalation in radiotherapy (RT), high-intensity focused ultrasound (HIFU) focal laser ablation (FAL), cryotherapy, or irreversible electroporation (IRE) [5]
Analysis of tumor volumes revealed that gross tumor volume (GTV)-MRI was statistically significant smaller than GTV based on PET images (GTV-PET)
Summary
Prostate cancer (PCa) is the most common tumor entity for men in North America [1] and Europe [2], and PCa incidence rates are rising steadily in Asian countries as well [3]. Multiparametric magnetic resonance imaging (mpMRI) is the current gold standard for PCa detection [4] but has been shown to miss pivotal tumor lesions and underestimates their volume [6, 7]. Instead prostate-specific membrane antigen positron emission tomography (PSMA-PET) is emerging as a promising technique to improve tumor lesion detection [8,9,10,11,12,13,14,15], focal therapy guidance [16], and non-invasive PCa characterization [17]. Tumor volumes delineated in PSMA-PET and mpMRI differed significantly, with smaller volumes in mpMRI [24, 25]
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