PRECISION MANAGEMENT OF LOCALIZED PROSTATE CANCER

Associations of PTEN and ERG with Magnetic Resonance Imaging Visibility and Assessment of Non-organ-confined Pathology and Biochemical Recurrence After Radical Prostatectomy

BACKGROUND

Diagnosing clinically significant prostate cancer (PCa) is challenging, but may be facilitated by biomarkers and multiparametric magnetic resonance imaging (MRI).

OBJECTIVE

To determine the association between biomarkers phosphatase and tensin homolog (PTEN) and ETS-related gene (ERG) with visible and invisible PCa lesions in MRI, and to predict biochemical recurrence (BCR) and non-organ-confined (non-OC) PCa by integrating clinical, MRI, and biomarker-related data.

DESIGN, SETTING, AND PARTICIPANTS

A retrospective analysis of a population-based cohort of men with PCa, who underwent preoperative MRI followed by radical prostatectomy (RP) during 2014-2015 in Helsinki University Hospital (n = 346), was conducted. A tissue microarray corresponding to the MRI-visible and MRI-invisible lesions in RP specimens was constructed and stained for PTEN and ERG.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Associations of PTEN and ERG with MRI-visible and MRI-invisible lesions were examined (Pearson's χ² test), and predictions of non-OC disease together with clinical and MRI parameters were determined (area under the receiver operating characteristic curve and logistic regression analyses). BCR prediction was analyzed by Kaplan-Meier and Cox proportional hazard analyses.

RESULTS AND LIMITATIONS

Patients with MRI-invisible lesions (n = 35) had less PTEN loss and ERG-positive expression compared with patients (n = 90) with MRI-visible lesions (17.2% vs 43.3% [p = 0.006]; 8.6% vs 20.0% [p = 0.125]). Patients with invisible lesions had better, but not statistically significantly improved, BCR-free survival probability in Kaplan-Meier analyses (p = 0.055). Rates of BCR (5.7% vs 21.1%; p = 0.039), extraprostatic extension (11.4% vs 44.6%; p < 0.001), seminal vesicle invasion (0% vs 21.1%; p = 0.003), and lymph node metastasis (0% vs 12.2%; p = 0.033) differed between the groups in favor of patients with MRI-invisible lesions. Biomarkers had no independent role in predicting non-OC disease or BCR. The short follow-up period was a limitation.

CONCLUSIONS

PTEN loss, BCR, and non-OC RP findings were more often encountered with MRI-visible lesions.

PATIENT SUMMARY

Magnetic resonance imaging (MRI) of the prostate misses some cancer lesions. MRI-invisible lesions seem to be less aggressive than MRI-visible lesions.

Assessment of the compliance with minimum acceptable technical parameters proposed by PI-RADS v2 guidelines in multiparametric prostate MRI acquisition in tertiary referral hospitals in the Republic of Turkey

PURPOSE

Although the clinical use of multiparametric prostate magnetic resonance imaging (mpMRI) is increasing, the adherence to parameters for mpMRI, which had been described in the Prostate Imaging-Reporting and Data System version 2 (PI-RADS v2) for an optimum image acquisition is unknown. In this paper, we aimed to determine the compliance with the minimum acceptable technical parameters for prostate mpMRI defined by PI-RADS v2 in tertiary care centers in Turkey.

METHODS

We sent a survey to all radiology departments of tertiary referral hospitals in Turkey (n=120) to evaluate their adherence to PI-RADS v2 technical specifications. Statistical analysis was performed using chi-square, Fisher exact, ANOVA, and the Student t tests. The cutoff values for image acquisition times were also determined with receiver operating characteristics (ROC) analysis. P values <0.05 were considered statistically significant.

RESULTS

One hundred and eleven clinics responded to our survey (response rate, 92.5%). Prostate MRI was reported to be performed in 61 centers, of which 26 (42.6%) used 3 T (Tesla) scanner while 35 (57.4%) used 1.5 T. The adherence to slice thickness, in-plane phase and frequency resolutions on T2-weighted imaging were 68.9%, 41%, and 9.8%, respectively. The adherence to the same parameters on diffusion-weighted imaging (DWI) were higher compared with T2-weighted imaging (85.2%, 62.3%, and 78.7%, respectively). In comparative analysis, the adherence to slice thickness, field of view (FOV) and in-plane phase resolution on T2-weighted imaging were higher for 3 T compared with 1.5 T scanners (P = 0.004, P = 0.041, and P = 0.001, respectively). T2-weighted imaging acquisition time was significantly longer for the centers that adhered to FOV (P = 0.034) and in-plane T2-weighted imaging phase resolution (P = 0.028). The DWI scan time was significantly longer when they adhered to DWI-FOV (P = 0.014) and b value ≥1400 s/mm2 (P = 0.008). The calculated cutoff of scan times were 220 s in T2-weighted imaging and 312 s in DWI to ensure the compliance with voxel sizes and b value criteria.

CONCLUSION

The tertiary referral centers in Turkey did not meet majority of the technical specifications of PI-RADS v2 during prostate MRI acquisition. Awareness to the minimum acceptable technical parameters of mpMRI should be increased to potentially improve the quality of prostate cancer imaging.

Low Abundance of Circulating Tumor DNA in Localized Prostate Cancer

PURPOSE

Despite decreased screening-based detection of clinically insignificant tumors, most diagnosed prostate cancers are still indolent, indicating a need for better strategies for detection of clinically significant disease before treatment. We hypothesized that patients with detectable circulating tumor DNA (ctDNA) were more likely to harbor aggressive disease.

METHODS

We applied ultra-low-pass whole-genome sequencing to profile cell-free DNA from 112 patients diagnosed with localized prostate cancer and performed targeted resequencing of plasma DNA for somatic mutations previously identified in matched solid tumor in nine cases. We also performed similar analyses of data from patients with metastatic prostate cancer.

RESULTS

In all cases of localized prostate cancer, even in clinically high-risk patients who subsequently had recurrent disease, ultra-low-pass whole-genome sequencing and targeted resequencing did not detect ctDNA in plasma acquired before surgery or before recurrence. In contrast, using both approaches, ctDNA was detected in patients with metastatic prostate cancer.

CONCLUSION

Our findings demonstrate clear differences between localized and advanced prostate cancer with respect to the dissemination and detectability of ctDNA. Because allele-specific alterations in ctDNA are below the threshold for detection in localized prostate cancer, other approaches to identify cell-free nucleic acids of tumor origin may demonstrate better specificity for aggressive disease.

Molecular correlates of intermediate- and high-risk localized prostate cancer

Clinicopathologic parameters, including Gleason score, remain the most validated prognostic factors for patients diagnosed with localized prostate cancer (PCa). However, patients of the same risk groups have exhibited heterogeneity of disease outcomes. To improve risk classification, multiple molecular risk classifiers have been developed, which were designed to inform beyond existing clinicopathologic classifiers. Alterations affecting tumor suppressors and oncogenes, such as PTEN, MYC, BRCA2, and TP53, which have been long associated with aggressive PCa, demonstrated grade-dependent frequency of alterations in localized PCas. In addition to these genetic hallmarks, several RNA-based commercial tests have been recently developed to help identify men who would benefit from earlier interventions. Large genomic studies also correlate germline genetic alterations and epigenetic features with adverse outcomes, further strengthening the link between the risk of metastasis and a stepwise accumulation of driver molecular lesions.