How accurate is 68Gallium-prostate specific membrane antigen positron emission tomography / computed tomography (68Ga-PSMA PET/CT) on primary lymph node staging before radical prostatectomy in intermediate and high risk prostate cancer? A study of patient- and lymph node- based analyses

Survival outcomes of patients treated with local therapy for nonmetastatic prostate cancer with high prostate-specific antigen concentrations

BACKGROUND

Patients with nonmetastatic prostate cancer (nmPCa) and high prostate-specific antigen (PSA) levels due to the high likelihood of metastasis pose a clinical dilemma regarding their optimal treatment and long-term outcomes after initial local therapy. We aimed to evaluate the oncologic outcomes of patients treated with radical prostatectomy (RP) or radiotherapy (RT) for nmPCa with high PSA levels.

METHODS

We queried the Surveillance, Epidemiology, and End Results (SEER) database to identify patients diagnosed with nmPCa who received RP or RT from 2004 through 2015. We included nmPCa patients with high PSA levels categorized as ≥50 and ≥98 ng/mL, the highest level recorded in SEER. We used the Kaplan-Meier method and Cox proportional hazards to analyze cancer-specific (CSS) and overall survival (OS).

RESULTS

We included 6177 patients with nmPCa and PSA ≥ 50 ng/mL at diagnosis; 1698 (27%) had PSA ≥ 98 ng/mL. Of these, 1658 (26.8%) underwent RP and 4519 (73.16%) patients received primary RT. Within a median of 113 months (interquartile range 74-150 months), the 5- and 10-year CSS estimates were 92.3% and 81.5% respectively; 10-year OS was 61%. In the PSA ≥ 98 ng/mL subgroup 5- and 10-year CSS estimates were 89.2% and 76%, respectively. In multivariable analyses for CSS, ISUP grade group (p < 0.001), N stage (p < 0.001), treatment with RP (hazard ratio [HR] = 0.60, 95% confidence interval [CI] 0.43-0.83, p < 0.001), and patient's age (p < 0.05) were associated with improved CSS. In the whole cohort of patients with PSA ≥ 50 ng/mL and RP subgroup, PSA failed to retain its independent prognostic value for CSS.

CONCLUSIONS

Patients treated with local therapy for nmPCa with very high PSA at diagnosis have relatively good long-term oncological outcomes. Therefore, among well-selected patients with nmPCa, high PSA levels alone should not preclude the use of radical local therapy. Potential selection bias limits inferences about the relative effectiveness of specific local therapies in this setting.

Calibrated Regression Models Based on the Risk of Clinical Nodal Metastasis Should be Used as Decision Aids for Prostate Cancer Staging to Reduce Unnecessary Imaging

INTRODUCTION

Radionuclide imaging will change the role of computed tomography and magnetic resonance imaging (CT/MRI) for prostate cancer (CaP) staging. Current guidelines recommend abdominopelvic imaging for new cases of CaP categorized as unfavorable intermediate risk (UIR) or higher. We assessed the performance characteristics of CT/MRI based on the National Comprehensive Cancer Network (NCCN) guidelines and developed a model that predicts cN1 disease using conventional imaging.

PATIENTS AND METHODS

We selected patients in the National Cancer Database diagnosed with CaP from 2010 to 2016 with available age, prostate specific antigen, clinical locoregional staging, biopsy Gleason grading, and core information. Multivariate logistic regression (MLR) was used on a undersampled training dataset using cN1 as the outcome. Performance characteristics were compared to those of the three most recent versions of the NCCN guidelines.

RESULTS

A total of 443,640 men were included, and 2.5% had cN1 disease. Using CT/MRI only, the current NCCN guidelines have a sensitivity of 99%, and the number needed to image (NNI) is 24. At the same sensitivity, the cN1 risk was 1.6% using the MLR. The NNI for UIR alone is 341. Using the MLR model and a threshold of 10%, the PPV is 10.3% and 64% of CTs/MRIs could be saved at a cost of missing 6% of cN1 patients (or 0.15% of all patients).

CONCLUSION

The NCCN guidelines are sensitive for detecting cN1 with CT/MRI, however, the number needed to image is 24. Obtaining CT/MRI for nodal staging when patients have a cN1 risk of 10% would reduce total imaging while still remaining sensitive. As novel PET tracers becomes increasingly used for initial CaP staging, well calibrated prediction models trained on the outcome of interest should be developed as decision aids for obtaining imaging.

Head-to-Head Comparison of 68Ga-PSMA-11 PET/CT and Multiparametric MRI for Pelvic Lymph Node Staging Prior to Radical Prostatectomy in Patients With Intermediate to High-Risk Prostate Cancer: A Meta-Analysis

PURPOSE

To compare the diagnostic performance of 68Ga-PSMA-11 PET/CT and mpMRI for pelvic lymph node staging prior to radical prostatectomy in prostate cancer (PCa) patients based on per patient data.

METHODS

PubMed and Embase databases were searched until October 2020 for eligible studies evaluating head-to-head comparison of 68Ga-PSMA-PET/CT and mpMRI for the detection of pelvic lymph node metastases (PLNMs) using pelvic lymph node dissection (PLND) as gold standard. The pooled sensitivity, specificity, and area under the summary receiver-operating characteristics curve (AUC) were determined for the two imaging modalities.

RESULTS

Nine studies with 640 patients were included. The pooled sensitivity, specificity, and AUC for 68Ga-PSMA-11 PET/CT vs. mpMRI were 0.71 (95% CI: 0.48-0.86) vs. 0.40 (95% CI: 0.16-0.71), 0.92 (95% CI: 0.88-0.95) vs. 0.92 (95% CI: 0.80-0.97), and 0.92 (95% CI: 0.88-0.95) vs. 0.82 (95% CI: 0.79-0.86), respectively. There was substantial heterogeneity for both imaging modalities, and meta-regression analysis revealed that the number of patients, prevalence of PLNMs, PSA level, reference standard, and risk classification might be the potential causes of heterogeneity.

CONCLUSION

This meta-analysis of head-to-head comparison studies confirms that there is a trend toward a higher sensitivity and diagnostic accuracy of 68Ga-PSMA-11 PET/CT compared to mpMRI for the detection of PLNMs in PCa patients. Nevertheless, according to current guidelines, PLND still needs to be recommended in case of negative results from 68Ga-PSMA-11 PET/CT due to significant risk of malignancy.