The Influence of Background Signal Intensity Changes on Cancer Detection in Prostate MRI

OBJECTIVE. The objective of this study was to develop a scoring system for background signal intensity changes or prostate homogeneity on prostate MRI and to assess these changes' influence on cancer detection. MATERIALS AND METHODS. This institutional review board-approved, HIPAA-compliant, retrospective study included 418 prostate MRI examinations in 385 men who subsequently underwent MRI-guided biopsy. The Likert score for suspicion of cancer assigned by the primary radiologist was extracted from the original report, and histopathologic workup of the biopsy cores served as the reference standard. Two readers assessed the amount of changes on T2-weighted sequences and assigned a predefined prostate signal-intensity homogeneity score of 1-5 (1 = poor, extensive changes; 5 = excellent, no changes). The sensitivity and specificity of Likert scores for detection of prostate cancer and clinically significant cancer (Gleason score >= 3+4) were estimated in and compared between subgroups of patients with different signal-intensity homogeneity scores (<= 2, 3, and >= 4). RESULTS. Interreader agreement on signal-intensity homogeneity scores was substantial (kappa = 0.783). Sensitivity for prostate cancer detection increased when scores were better (i.e., higher) (reader 1, from 0.41 to 0.71; reader 2, from 0.53 to 0.73; p <= 0.007, both readers). In the detection of significant cancer (Gleason score >= 3+4), sensitivity also increased with higher signal-intensity scores (reader 1, from 0.50 to 0.82; reader 2, from 0.63 to 0.86; p <= 0.028), though specificity decreased significantly for one reader (from 0.67 to 0.38; p = 0.009). CONCLUSION. Background signal-intensity changes on T2-weighted images significantly limit prostate cancer detection. The proposed scoring system could improve the standardization of prostate MRI reporting and provide guidance for applying prostate MRI results appropriately in clinical decision-making.