Table 1.
Characteristics of 37 studies included in the systematic review.
| Characteristics | Studies, n | Patients (average over the number of studies), n | ||
| Study type | ||||
| Prospective | 8 | 2210 (276.25) | ||
| Retrospective | 29 | 6414 (221.17) | ||
| Data set type | ||||
| Private data set | 33 | 7760 (235.15) | ||
| Public database (SPIE-AAPM-NCIa PROSTATEx challenge) | 2 | 399 (199.5) | ||
| Mixed (private and public) data set | 2 | 465 (232.5) | ||
| Classification algorithms | ||||
| Random forest | 4 | 1621(405.25) | ||
| Regression-based models | 20 | 4678 (233.9) | ||
| Partial least squares discriminant analysis (PLS-DA) | 2 | 180 (90) | ||
| Linear discriminant analysis (LDA) | 1 | 53 | ||
| Support vector machine (SVM) | 2 | 65 (32.5) | ||
| Classification and regression tree (CART) | 1 | 67 | ||
| Artificial neural networks (ANNs) | 2 | 1012 (506) | ||
| Deep neural networks (DNNs) | 1 | 195 | ||
| Convolutional neural networks (CNNs) | 3 | 696 (232) | ||
| Deep learning: SNCSAEb | 1 | 57 | ||
| Predictor type | ||||
| Multiparametric MRIc | 20 | 5058 (252.9) | ||
| Genetic or molecular biomarker | 13 | 3132 (240.92) | ||
| Urine | 6 | 930 (155) | ||
| Serum | 3 | 901 (300.3) | ||
| Semen | 2 | 108 (54) | ||
| Tissue | 2 | 800 (400) | ||
| Clinical data | 4 | 2812 (703) | ||
| Validation method | ||||
| Internal validation | 29 | 6540 (225.52) | ||
| External validation | 3 | 1380 (460) | ||
| Internal and external validation | 1 | 364 | ||
| Unknown | 5 | 704 (140.8) | ||
aSPIE-AAPM-NCI: International Society for Optics and Photonics–American Association of Physicists in Medicine–National Cancer Institute.
bSNCSAE: stacked nonnegativity constraint sparse autoencoders.
cMRI: magnetic resonance imaging.