Prostate cancer (PCa) is one of the most frequently diagnosed malignancies of men in the world. Due to a variety of treatment options in different risk groups, proper diagnostic and risk stratification is pivotal in treatment of PCa. The development of precise medical imaging procedures simultaneously to improvements in big data analysis has led to the establishment of radiomics - a computer-based method of extracting and analyzing image features quantitatively. This approach bears the potential to assess and improve PCa detection, tissue characterization and clinical outcome prediction. This article gives an overview on the current aspects of methodology and systematically reviews available literature on radiomics in PCa patients, showing its potential for personalized therapy approaches. The qualitative synthesis includes all imaging modalities and focuses on validated studies, putting forward future directions.

Purpose: Accurate 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. Methods: One 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. Results: In 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). Conclusion: MpMRI 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.

Technical advances in radiotherapy (RT) treatment planning and delivery have substantially changed RT concepts for primary prostate cancer (PCa) by (i) enabling a reduction of treatment time, and by (ii) enabling safe delivery of high RT doses. Several studies proposed a dose–response relationship for patients with primary PCa and especially in patients with high-risk features, as dose escalation leads to improved tumor control. In parallel to the improvements in RT techniques, diagnostic imaging techniques like multiparametric magnetic resonance imaging (mpMRI) and positron-emission tomography targeting prostate-specific-membrane antigen (PSMA-PET) evolved and enable an accurate depiction of the intraprostatic tumor mass for the first time. The HypoFocal-SBRT study combines ultra-hypofractionated RT/stereotactic body RT, with focal RT dose escalation on intraprostatic tumor sides by applying state of the art diagnostic imaging and most modern RT concepts. This novel strategy will be compared with moderate hypofractionated RT (MHRT), one option for the curative primary treatment of PCa, which has been proven by several prospective trials and is recommended and carried out worldwide. We suspect an increase in relapse-free survival (RFS), and we will assess quality of life in order to detect potential changes.

The bicentric HypoFocal phase 2 trial investigates the implementation of molecular imaging with positron-emission tomography targeting prostate-specific membrane antigen (PSMA-PET) into modern focal dose-escalation radiation therapy (RT) concepts in 2 nonrandomized arms. We present the planned safety analysis after 6 months of follow-up. Intermediate- and high-risk localized primary prostate cancer patients staged with multiparametric magnet resonance tomography and PSMA-PET were either treated with focal dose-escalated moderately hypofractionated RT (arm A) or single fraction high-dose-rate brachytherapy followed by external beam RT (arm B). PSMA-PET was used in addition to primary prostate cancer to define the intraprostatic gross tumor volume. Gastrointestinal and genitourinary toxicities were assessed according to Common Toxicity Criteria for Adverse Events (version 5.0) criteria. International Prostate Symptom Score was measured and quality of life assessed with European Organisation for Research and Treatment of Cancer questionnaires QLQ-PR25/-PR30. We enrolled 25 patients in each study arm. The implementation of PET-information led to large median volumes for dose escalation: 10.2 mL in arm A and 6.8 mL in Arm B. RT dose-escalation was feasible in all patients of arm A with up to 75 Gy (20 fractions) and in 23 patients with up to 19 Gy (1 fraction) in arm B. Toxicities, International Prostate Symptom Scores, and European Organisation for Research and Treatment of Cancer quality of life scores were not significantly different between baselines and 6 months follow-up in both arms. No grade 3 toxicities were observed at 6 months follow-up. This is the first prospective data supporting the feasibility of PSMA-PET-implementation into definitive focal dose-escalated RT. Patients maintained a good quality of life and a low toxicity profile after 6 months of follow-up.

Purpose: Accurate contouring of intraprostatic gross tumor volume (GTV) is pivotal for successful delivery of focal therapies and for biopsy guidance in patients with primary prostate cancer (PCa). Contouring of GTVs, using 18-Fluor labeled tracer prostate specific membrane antigen positron emission tomography ([¹⁸F]PSMA-1007/PET) has not been examined yet.Patients and Methods: Ten Patients with primary PCa who underwent [¹⁸F]PSMA-1007 PET followed by radical prostatectomy were prospectively enrolled. Coregistered histopathological gross tumor volume (GTV-Histo) was used as standard of reference. PSMA-PET images were contoured on two ways: (1) manual contouring with PET scaling SUVmin-max: 0–10 was performed by three teams with different levels of experience. Team 1 repeated contouring at a different time point, resulting in n = 4 manual contours. (2) Semi-automatic contouring approaches using SUVmax thresholds of 20–50% were performed. Interobserver agreement was assessed for manual contouring by calculating the Dice Similarity Coefficient (DSC) and for all approaches sensitivity, specificity were calculated by dividing the prostate in each CT slice into four equal quadrants under consideration of histopathology as standard of reference.Results: Manual contouring yielded an excellent interobserver agreement with a median DSC of 0.90 (range 0.87–0.94). Volumes derived from scaling SUVmin-max 0–10 showed no statistically significant difference from GTV-Histo and high sensitivities (median 87%, range 84–90%) and specificities (median 96%, range 96–100%). GTVs using semi-automatic segmentation applying a threshold of 20–40% of SUVmax showed no significant difference in absolute volumes to GTV-Histo, GTV-SUV50% was significantly smaller. Best performing semi-automatic contour (GTV-SUV20%) achieved high sensitivity (median 93%) and specificity (median 96%). There was no statistically significant difference to SUVmin-max 0–10.Conclusion: Manual contouring with PET scaling SUVmin-max 0–10 and semi-automatic contouring applying a threshold of 20% of SUVmax achieved high sensitivities and very high specificities and are recommended for [¹⁸F]PSMA-1007 PET based focal therapy approaches. Providing high specificities, semi-automatic approaches applying thresholds of 30–40% of SUVmax are recommend for biopsy guidance.