Optimal Method for Reporting Prostate Cancer Grade in MRI-targeted Biopsies

Prostate magnetic resonance imaging-targeted biopsy global grade correlates better than highest grade with prostatectomy grade

BACKGROUND

Magnetic resonance imaging (MRI)-targeted prostate biopsy has become an increasingly common method of diagnosing prostate cancer. A previous study from our institution demonstrated that the biopsy global Grade Group (gGG, aggregate GG of all positive cores) and highest Grade Group (hGG in any core) both show substantial concordance with the Grade Group at radical prostatectomy (RPGG) while the discordance predominantly consists of upgrading in gGG and downgrading in hGG. We performed a larger cohort study focused on biopsy cases in which gGG and hGG differ, to determine their relative concordance with RPGG.

METHODS

We conducted a retrospective review of radical prostatectomy specimens with prior MRI-targeted biopsies from our institution between 2016 and 2020. Separate gGG and hGG were assigned to each MRI-targeted lesion. Targeted lesions with different gGG versus hGG were segregated from those with identical gGG and hGG. The concordance of biopsy GG with RPGG was evaluated using κ coefficient analysis.

RESULTS

Of the 489 lesions with MRI-targeted biopsies, 82 (17%) differed in gGG versus hGG. The gGG of 46 (56%), 33 (40%), and 3 (4%) lesions were unchanged, upgraded, and downgraded at radical prostatectomy, respectively (κ= 0.302, weighted κ = 0.334). The hGG of 24 (29%), 9 (11%), and 49 (60%) lesions were unchanged, upgraded, and downgraded at radical prostatectomy, respectively (κ = 0.040, weighted κ = 0.198). When stratified by the biopsy GG, gGG showed the highest concordance in GG2 (61%) and GG3 (54%) lesions. The hGG resulted in substantial downgrading (60%) with less optimal concordance regardless of the biopsy GG. Neither the prebiopsy prostate specific antigen level nor the PI-RADS score was predictive of upgrading of gGG.

CONCLUSIONS

When gGG and hGG differ, gGG method more accurately predicts the RPGG than hGG, particularly in GG2 and GG3 lesions which comprised the majority of targeted lesions.

Biopsy-Integrated 3D Magnetic Resonance Imaging Modeling of Prostate Cancer and Its Application for Gleason Grade and Tumor Laterality Assessment

CONTEXT.—

Grade Group assessed using Gleason combined score and tumor extent is a main determinant for risk stratification and therapeutic planning of prostate cancer.

OBJECTIVE.—

To develop a 3-dimensional magnetic resonance imaging (MRI) model regarding Grade Group and tumor extent in collaboration with uroradiologists and uropathologists for optimal treatment planning for prostate cancer.

DESIGN.—

We studied the data from 83 patients with prostate cancer who underwent multiparametric MRI and subsequent MRI-transrectal ultrasound fusion biopsy and radical prostatectomy. A 3-dimensional MRI model was constructed by integrating topographic information of MRI-based segmented lesions, biopsy paths, and histopathologic information of biopsy specimens. The multiparametric MRI-integrated Grade Group and laterality were assessed by using the 3-dimensional MRI model and compared with the radical prostatectomy specimen.

RESULTS.—

The MRI-defined index tumor was concordant with radical prostatectomy in 94.7% (72 of 76) of cases. The multiparametric MRI-integrated Grade Group revealed the highest agreement (weighted κ, 0.545) and a significantly higher concordance rate (57.9%) than the targeted (47.8%, P = .008) and systematic (39.4%, P = .01) biopsies. The multiparametric MRI-integrated Grade Group showed significantly less downgrading rates than the combined biopsy (P = .001), without significant differences in upgrading rate (P = .06). The 3-dimensional multiparametric MRI model estimated tumor laterality in 66.2% (55 of 83) of cases, and contralateral clinically significant cancer was missed in 9.6% (8 of 83) of cases. The tumor length measured by multiparametric MRI best correlated with radical prostatectomy as compared with the biopsy-defined length.

CONCLUSIONS.—

The 3-dimensional model incorporating MRI and MRI-transrectal ultrasound fusion biopsy information easily recognized the spatial distribution of MRI-visible and MRI-nonvisible cancer and provided better Grade Group correlation with radical prostatectomy specimens but still requires validation.

Diagnosis and Pathologic Reporting of Prostate Cancer in the Era of MRI-Targeted Prostate Biopsy

Historically, the detection of prostate cancer relied upon a systematic yet random sampling of the prostate by transrectal ultrasound guided biopsy. This approach was a nontargeted technique that led to the under detection of cancers at biopsy and the upgrading of cancers at radical prostatectomy. Multiparametric MRI-targeted prostate biopsy allows for an image-directed approach to the identification of prostate cancer. MRI-targeted biopsy of the prostate is superior for the detection of clinically significant prostate cancer. As this technique has become more prevalent among urologists, pathologists need to recognize how this development impacts cancer diagnosis and reporting.

Optimized grade group for reporting prostate cancer grade in systematic and MRI-targeted biopsies

PURPOSE

To explore an optimized grade group (oGG) criterion from systematic biopsies (SB) and targeted biopsies (TB) and offer a better prediction of radical prostatectomy (RP) grade group (GG).

METHODS

Positive needles were collected from 146 patients who underwent SB + TB followed by RP. The grade was assigned for two different kinds of biopsies with five GG criteria: (1) global GG (gGG); (2) most common GG (most common GG from SB + TB, mGG); (3) highest GG (highest numerical GG from SB + TB, hGG); (4) largest volume/linear length cancer GG (defined as GG from the SB + TB with the largest length of cancer in a needle, lGG). These biopsy grades were compared (equivalence, upgrade, or downgrade) with the final grade of the RP lesion, using weighted κ coefficients; (5) Then the best agreement of the (2) (3) (4) grading scores from SB or TB was combined to introduce an oGG.

RESULTS

In this study, gGG showed generally poor agreement (47.2%) with RP GG (weighted κ: 0.43). Using the three criteria (mGG, hGG, and lGG) of SB, mGG had the best agreement (55.5%, weighted κ: 0.46), while hGG and lGG had a lower agreement (48.6% and 48.6%, weighted κ: 0.42 and 0.38). Using the three criteria (mGG, hGG and lGG) of TB: lGG had the best agreement (56.8%, weighted κ: 0.43), while mGG and hGG had lower agreement (50.0% and 49.3%, weighted κ: 0.40 and 0.40); Then oGG was generated (higher GG between mGG of SB and lGG of TB) and the agreement of oGG increased to 59.6% and weighted κ was 0.49. Additionally, oGG had a lower upgrade rate than gGG, while the downgrade rate remained unchanged.

CONCLUSIONS

oGG showed better agreement with RP GG than gGG. oGG had a lower upgrade rate than gGG, while downgrade rate remained unchanged.