Characteristics of Detected and Missed Prostate Cancer Foci on 3-T Multiparametric MRI Using an Endorectal Coil Correlated With Whole-Mount Thin-Section Histopathology

Abstract

Objective: The objective of this study was to determine the characteristics of prostate cancer foci missed on 3-T multiparametric MRI performed with an endorectal coil.

Materials and methods: The MRI examinations of 122 patients who underwent 3-T multiparametric MRI of the prostate with an endorectal coil were compared with whole-mount histopathology obtained after radical prostatectomy. The mean age of the patients was 60.6 years (SD, 7.6 years), and the mean prostate-specific antigen value was 7.2 ng/mL (SD, 5.9 ng/mL). The clinical, multiparametric MRI (i.e., T2-weighted imaging, diffusion-weighted imaging, and dynamic contrast-enhanced imaging), and histopathologic features were obtained. After an independent review, two blinded genitourinary radiologists matched each case with a genitourinary pathologist. A structured reporting system was used to classify the multiparametric MRI features of each MRI-detected lesion. A chi-square analysis was performed for categoric variables, and the t test was performed for continuous variables.

Results: On whole-mount histopathology, 285 prostate cancer foci were detected in 122 patients. Of the 285 cancer foci detected at histopathology, 153 (53.3%) were missed on MRI and 132 (46.7%) were detected on MRI. Of the missed lesions, 75.2% were low-grade prostate cancer. Multiparametric MRI had a significantly higher sensitivity for prostate cancer foci 1 cm or larger than for subcentimeter foci (81.1% vs 18.9%, respectively; p < 0.001), for lesions with a Gleason score of 7 or greater than for lesions with a Gleason score of 6 (72.7% vs 27.3%; p < 0.01), and for index lesions than for satellite lesions (80.3% vs 20.8%; p < 0.01). The 3-T multiparametric MRI examinations showed a higher detection rate for lesions in the midgland or base of the gland compared with lesions in the apex (52.3% vs 22.0%, respectively; p < 0.01).

Conclusion: Compared with the prostate cancer lesions that were detected on multiparametric MRI, the prostate cancer lesions that were missed were significantly smaller, were more likely to be low-grade lesions (i.e., Gleason score of 6), were more commonly satellite lesions, and were more likely to be located in the prostatic apex.

Keywords: multiparametric prostate MRI; prostate cancer.

Fig. 1

Graphic shows sequence of tasks for radiologic-pathologic review process used for this study.

Fig. 2

Bar graph shows percentage of prostate tumors detected on MRI stratified by tumor size and by sum of Gleason scores (p < 0.01).

Fig. 3

Bar graph shows percentage of prostate tumors detected on MRI stratified by index tumors (vs secondary tumors) and by Gleason score (p < 0.01).

Fig. 4

Bar graph shows percentage of prostate tumors detected on MRI stratified by location and by Gleason score (p < 0.01).

Fig. 5

67-year-old man with elevated prostate-specific antigen value. A, T2-weighted image shows hypointense lesion (arrow) in left peripheral zone. B, Diffusion-weighted image shows diffusion restriction (arrow) in area corresponding to hypointense lesion on T2-weighted image (A). C, Dynamic contrast-enhanced MR image shows perfusion abnormality (arrow) in area corresponding to hypointense lesion on T2-weighted image (A). D and E, Patient underwent robot-assisted laparoscopic prostatectomy. Photomicrographs of thin sections from whole-mount preparation of specimen obtained at radical prostatectomy show index lesion (arrow, D) with Gleason score of 3 + 4 that corresponds to lesion shown by multiparametric MRI. However, multiple subcentimeter lesions with Gleason score of 3 + 3 (arrowheads) in right midgland and apex were missed on multiparametric MRI.