Prostate-Specific Membrane Antigen Positron Emission Tomography can be used to detect pelvic lymph nodes in prostate cancer

1. For the detection of pelvic nodal metastases in men with intermediate-to high-risk prostate cancer, using the 68Ga-PSMA-11 PET scan, the sensitivity and specificity were 0.40 and 0.95

2. The positive predictive value and the negative predictive value were 0.75 and 0.81

Evidence Rating Level: 1 (Excellent)

Study Rundown: Positron emission tomography (PET) targeting prostate-specific membrane antigen (PSMA) can increase diagnostic accuracy to help better detect pelvic nodal metastases at initial staging. Detecting pelvic nodal metastases at initial staging can guide clinicians when determining the appropriateness of radial prostatectomy. This study aimed to evaluate the accuracy of 68Ga-PSMA-11 PET imaging to detect pelvic nodal metastases compared to histopathology in intermediate- to high-risk prostate cancer patients being considered for radical prostatectomy. 68Ga-PSMA-11 PET imaging had lower sensitivity compared to the predefined threshold but had high specificity. The positive predictive value (PPV) was high at 0.75 and the negative predictive value (NPV) was 0.81. One of the main limitations include having lower number of the study population included in the efficacy analysis due to patients receiving other therapies instead of prostatectomy. This could have contributed to the lower sensitivity rate since patients with more extensive nodes were treated using alternative therapies. Another limitation is the open label study design of the study, which allowed clinicians to modify therapy based on the PET scan results. Overall, this study demonstrated that a positive 68Ga-PSMA-11 PET imaging could be a beneficial tool to help clinicians detect pelvic nodal metastasis as a true positive in intermediate- to high-risk prostate cancer patients considering prostatectomy. However, it may not be reliable in ruling out nodal metastases and may require further studies.

Click to read the study in JAMA Oncology

Click to read an accompanying invited commentary in JAMA Oncology

Relevant Reading: Outcomes of primary lymph node staging of intermediate and high risk prostate cancer with 68Ga-PSMA positron emission tomography/computerized tomography compared to histological correlation of pelvic lymph node pathology

In-Depth [prospective cohort]: This was a phase 3, prospective, multicenter, single-arm, open label imaging trial of 764 patients at 2 institutions in the United States. Eligible patients included those who had intermediate- to high-risk prostate cancer and were considered for radical prostatectomy. Patients were excluded if they received prostate cancer therapy prior to prostatectomy. All patients received an imaging scan with 3-7 mCi of 68Ga-PSMA-11 PET. However, only patients who received radical prostatectomy were included in the efficacy analysis. The primary endpoint was the sensitivity and specificity of the 68Ga-PSMA-11 PET to detect pelvic nodal metastases compared to histopathology. Each imaging scan of the patients who were included in the efficacy analysis was interpreted by 3 blinded, independent central readers that were not involved in the study design and data collection process. The sensitivity and specificity were 0.40 (95% confidence interval [CI]: 0.34-0.46) and 0.95 (95% CI: 0.92-0.97). The positive predictive value (PPV) and the negative predictive value (NPV) were 0.75 (95% CI: 0.92-0.97) and 0.81 (95% CI: 0.76-0.85. Grade 1 adverse events were reported in 6% of the patients and none required further intervention. Commonly reported adverse events were rash and nausea.

Image: PD

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