AUA 2018: Diagnostic Value of 68GA-Labelled PSMA PET/CT Imaging for Renal Cell Carcinoma

San Francisco, CA ( PSMA (prostate specific membrane antigen) is a targetable receptor that has high specificity for prostate cancer, and as such, PSMA PET scans have been gaining significant traction in the management of recurrent prostate cancer to identify low-volume recurrent disease. Yet, despite its high specificity for prostate cancer, it is known to be expressed in other benign tissues – and occasionally other malignancies.

In this study, the authors note that prostate-specific membrane antigen (PSMA) is overexpressed in tumor with increased neovasculaturity, including patients with renal cell carcinoma (RCC). Mutations leading to RCC are strongly associated with increased neovascularity, and many current systemic therapies for RCC exploit this.

The authors present a small series of 38 patients, of which 18 patients underwent 68Ga-PSMA PET/CT. They had this scan prior to surgical management with robot-assisted laparoscopic radical or partial nephrectomy. The remaining 20 patients were diagnosed with metastases after 68Ga-PSMA PET/CT scan. SUVmax was calculated for both primary RCCs and PET-positive metastatic lesions. 

This study is in no way randomized. It is merely a proof of principle. Hence, there is not comparator study.   The authors found that the mean SUVmax of primary RCCs (18 patients) was 9.46±7.82 (Range 1.2-26.79). Clear cell RCC presented higher PSMA uptake (SUVmax: 16.68±5.90) while other pathological types displayed a low SUVmax value (less than 10). 

In the cohort of 20 patients with metastatic RCC, they found that metastases in patients with clear cell RCC showed intense uptake in bone and lymph nodes. Small lung metastases were PET-negative. Similar to primary RCC, 68Ga-labelled PSMA PET/CT was not sensitive for metastatic lesions of non-clear cell RCC.

Based on this, the authors suggest that 68Ga-labelled PSMA PET/CT may have a role in the staging of primary clear cell RCC and metastatic evaluation for patients with clear cell RCC. 

While interesting in concept, this remains a proof of principle study with limited long-term implications. Randomized studies need to be done to demonstrate an added benefit of PET/CT above and beyond routine staging studies.

Presented by: Chengwei Zhang, Nanjing, China
Co-Author: Xiaozhi Zhao, Zang Shiming, Feng Wang, Hongqian Guo

Written by: Thenappan Chandrasekar, MD, Clinical Fellow, University of Toronto, @tchandra_uromd at the 2018 AUA Annual Meeting - May 18 - 21, 2018 – San Francisco, CA USA
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