Early response assessment to targeted therapy in metastatic clear cell renal cancer using ⁶⁸Ga-PSMA-11 PET/CT and comparison with CECT: a feasibility study

Contrast-enhanced computed tomography (CECT) underestimates the response to targeted therapy in metastatic renal cell cancer (mRCC) using Response Assessment Criteria In Solid Tumors (RECIST) v1.1, creating an unmet need for better imaging biomarkers for early response assessment. This study explores the feasibility of early response assessment to targeted therapy in metastatic clear cell RCC (ccRCC) using ⁶⁸Ga-PSMA-11 PET/CT.

After informed consent, adult patients with biopsy-proven metastatic ccRCC planned for targeted therapy were recruited in this prospective observational pilot study from May 2021 to December 2022. ⁶⁸Ga-PSMA-11 PET/CT was conducted at baseline and one and three months post-treatment. The concordance between PET and CT responses at one and three months was analysed. Follow-up and comparison of progression-free survival (PFS) between responders and non-responders on PET and CT was done.

Twenty-one metastatic ccRCC patients were included in the final analysis. The response assessment on PET and CT was discordant in 15 out of 21 patients (~ 71%) at one month and in nine out of 21 patients (~ 43%) at three months. There was no significant difference between the median PFS of responders vs non-responders on CT at one (14 m vs. 12 m, p = 0.9) and three months (14 m vs. 12 m, p = 0.6). However, a higher difference in median PFS was observed between responders and non-responders on PET at one (PFS 14 m vs. 1 m, p < 0.001) and three months (PFS 14 m vs. 3 m, p = 0.28), respectively.

Early response assessment with ⁶⁸Ga-PSMA-11 PET/CT is feasible and provides more accurate prognostic information than CECT in metastatic clear cell RCC patients undergoing targeted therapy.

Trial registration number

CTRI/2021/05/033805 (date of registration: 25/05/21)