Intra-individual comparison of prostate-specific membrane antigen positron emission tomography/computed tomography versus bone scan in detecting skeletal metastasis at prostate cancer diagnosis

OBJECTIVES

To compare the diagnostic performance and radiological staging impact of 68 Ga-prostate-specific membrane antigen positron emission tomography/computed tomography (PSMA PET/CT) compared to 99 Tc whole-body bone scan (WBBS) for the detection of skeletal metastasis in the primary staging of prostate cancer (PCa).

PATIENTS AND METHODS

A prospective institutional database was retrospectively examined for patients who underwent both PSMA PET and WBBS within a 1 week interval for PCa primary staging. Lesions were categorised as 'negative', 'equivocal', or 'definite' based on nuclear medicine physician interpretation. Metastatic burden was characterised for each imaging modality according to three groups: (i) local disease (no skeletal metastases), (ii) oligometastatic disease (three or fewer skeletal metastases), or (iii) polymetastatic disease (more than three skeletal metastases).

RESULTS

There were 667 patients included. The median (interquartile range) prostate-specific antigen level was 9.2 (6.2-16) ng/mL and 60% of patients were high risk according to a modified D'Amico risk classification. The overall distribution of skeletal metastasis detection changed across the two scans overall (P = 0.003), being maintained within high-risk (P = 0.030) and low-risk (P = 0.018) groups. PSMA PET/CT identified more definite skeletal metastases compared to WBBS overall (10.3% vs 7.3%), and according to risk grouping (high: 12% vs 9%, intermediate: 4% vs 1%). Upstaging was more common with PSMA PET/CT than WBBS (P = 0.001). The maximum standardised uptake value (SUVmax ) of the primary tumour was associated with upstaging of skeletal metastases on PSMA PET/CT (P = 0.025), while age was associated with upstaging on WBBS (P = 0.021). The SUVmax of the primary tumour and metastases were both higher according to extent of metastatic disease (P = 0.001 and P < 0.001, respectively).

CONCLUSIONS

More skeletal metastases were detected with PSMA PET/CT than WBBS, resulting in a higher upstaging rate mostly in high-risk patients. The SUVmax of the primary tumour and metastases was associated with upstaging.

Fluorine-18-labelled Prostate-specific Membrane Antigen Positron Emission Tomography/Computed Tomography or Magnetic Resonance Imaging to Diagnose and Localise Prostate Cancer. A Prospective Single-arm Paired Comparison (PEDAL)

BACKGROUND AND OBJECTIVE

Multiparametric magnetic resonance imaging (mpMRI) of the prostate is used for prostate cancer diagnosis. However, mpMRI has lower sensitivity for small tumours. Prostate-specific membrane antigen positron emission tomography/computed tomography (PSMA-PET/CT) offers increased sensitivity over conventional imaging. This study aims to determine whether the diagnostic accuracy of 18F-DCFPyL PSMA-PET/CT was superior to that of mpMRI for detecting prostate cancer (PCa) at biopsy.

METHODS

Between 2020 and 2021, a prospective multicentre single-arm phase 3 imaging trial enrolled patients with clinical suspicion for PCa to have both mpMRI and PSMA-PET/CT (thorax to thigh), with reviewers blinded to the results of other imaging. Multiparametric MRI was considered positive for Prostate Imaging Reporting and Data System (PIRADS) 3-5. PSMA-PET/CT was assessed quantitatively (positive maximum standardised uptake value [SUVmax] >7) and qualitatively (five-point lexicon of certainty). Patients underwent targeted and systematic biopsy, with the technique at the discretion of the treating urologist. Clinically significant PCa (csPCa) was defined as International Society of Urological Pathology grade group (GG) ≥2. The primary outcome was the diagnostic accuracy for detecting PCa, reported as sensitivity, specificity, negative predictive value (NPV), and area under the curve (AUC) of the receiver operating curve. The secondary endpoints included a comparison of the diagnostic accuracy for detecting csPCa, assessing gains in combining PMSA-PET/CT with mpMRI to mpMRI alone.

KEY FINDINGS AND LIMITATIONS

Of the 236 patients completing both mpMRI and PSMA-PET/CT, 184 (76.7%) had biopsy. Biopsy histology was benign (n = 73), GG 1 (n = 27), and GG ≥2 (n = 84). The diagnostic accuracy of mpMRI for detecting PCa (AUC 0.76; 95% confidence interval [CI] 0.69, 0.82) was higher than that of PSMA-PET/CT (AUC 0.63; 95% CI 0.56, 0.70, p = 0.03). The diagnostic accuracy of mpMRI for detecting csPCa (AUC 0.72; 95% CI 0.67, 0.78) was higher than that of PSMA-PET/CT (AUC 0.62; 95% CI 0.55, 0.69) but not statistically significant (p = 0.27). A combination of PSMA-PET/CT and mpMRI showed excellent sensitivity (98.8%, 95% CI 93.5%, 100%) and NPV (96%, 95% CI 79.6%, 99.9%) over mpMRI alone (86.9% and 80.7%, respectively, p = 0.01). Thirty-two patients (13.6%) had metastatic disease. They tended to be older (68.4 vs 65.1 yr, p = 0.023), and have higher prostate-specific antigen (PSA; median PSA 9.6 vs 6.2ng/ml, p < 0.001) and abnormal prostate on digital rectal examination (78.2% vs 44.1%, p < 0.001).

CONCLUSIONS AND CLINICAL IMPLICATIONS

Multiparametric MRI had superior diagnostic accuracy to PSMA-PET/CT for detecting PCa, though the difference is not significant in case of csPCa detection. A combination of mpMRI and PSMA-PET/CT showed improved sensitivity and NPV. PSMA-PET/CT could be considered for diagnostic use in patients unable to have mpMRI or those with concerning clinical features but negative mpMRI.

PATIENT SUMMARY

In this trial, we compared the ability of 18F-labelled prostate-specific membrane antigen positron emission tomography/computed tomography (PSMA-PET/CT) with that of multiparametric magnetic resonance imaging (mpMRI) to diagnose prostate cancer by biopsy in a prostate-specific antigen screening population. We found that MRI was superior to PSMA to diagnose prostate cancer, though there was no difference in ability to diagnose clinically significant prostate cancer. PSMA-PET/CT could be considered for diagnostic use in patients unable to have mpMRI or those with concerning clinical features but negative mpMRI. Combining MRI with PSMA-PET increases the negative predictive value over MRI alone and may help men avoid invasive prostate biopsy.

Surgical Management of Organ-Confined Prostate Cancer with Review of Literature and Evolving Evidence

Prostate cancer is the most common solid organ malignancy in men in the USA with an annual incidence of 105 and an annual mortality rate of 19 per 100,000 people. With the advent of PSA screening, the majority of prostate cancer diagnosed is organ confined. Recent studies including the SPCG-4 and PIVOT trials have demonstrated a survival benefit for those undergoing active treatment for localized prostate cancer. The foremost surgical option has been radical prostatectomy (RP). The gold standard has been open radical retropubic prostatectomy (RRP); however, minimally invasive approaches including laparoscopic and robotic approaches are commonplace and increasing in popularity. We aim to describe the surgical options for the treatment of localized prostate cancer by reviewing the literature. A review of the literature was undertaken using MEDLINE and PubMed. Articles addressing the topic of radical prostatectomy by open, laparoscopic and robotic approaches were selected. Studies comparing the different modalities were also identified. These articles were reviewed for data pertaining to perioperative, oncological and functional outcomes. There is a paucity of randomized studies comparing the three modalities. The published data has demonstrated a benefit in favour of robotically assisted laparoscopic prostatectomy (RALP) over laparoscopic radical prostatectomy (LRP) and traditional open RRP in perioperative outcomes. When reviewing the best-reported outcomes for RALP compared to LRP and RRP, operative times are lower (105 vs. 138 vs. 138 min), estimated blood loss rates are lower (111 vs. 200 vs. 300 ml) and blood transfusion rates are lower as in the length of stay (1 vs. 2 vs. 2.3 days) and overall complication rates (4.3 vs. 5 vs. 20%). Similarly, when reviewing functional outcomes, RALP compared to LRP was not inferior. At 12 months, the reported continence was 97 vs. 94 vs. 89% and potency was 94 vs. 77 vs. 90%. In comparative studies, however, these differences did not always meet statistical significance. With respect to oncological outcomes, there was no clear evidence of superiority of one modality over another. RALP is now the most common modality for surgical treatment of organ-confined prostate cancer. Individual series appear to support better perioperative outcomes and perhaps quicker return to functional outcomes. There does not appear to be a clear advantage to date in oncological parameters; however, RALP does not appear to be inferior to either LRP or RRP. It is anticipated that further high quality randomized studies will shed more light on the clinical and statistical significance in the comparison between these modalities.