#0512

Performance of 68Ga-PSMA-11 PET/CT for diagnosing tumor thrombus and predicting response to pembrolizumab and axitinib in patients with renal cell carcinoma: a pilot, retrospective study

S. Chen¹, B. Lin¹, S. Chen¹, N. Xu¹

¹The First Affiliated Hospital of Fujian Medical University, Fuzhou, China

Introduction:

To investigate the performance of 68Ga-prostate-specific membrane antigen-11 positron emission tomography/computed tomography (68Ga-PSMA-11 PET/CT) for diagnosing tumor thrombus (TT) and predicting response to pembrolizumab and axitinib in clear cell renal cell carcinoma (ccRCC) with TT.

Material and methods:

162 renal cell carcinoma patients who underwent 68Ga-PSMA-11 PET/CT were included; among them, 31 ccRCC patients (22 male; mean age 55.90±13.36 years) with TT received a median of five treatment cycles of pembrolizumab and axitinib. The response to neoadjuvant therapy was evaluated according to the RECIST 1.1 criteria, and the diagnostic performance was assessed through the area under the curve (AUC).

Results:

The sensitivity, specificity, accuracy, positive predictive value, negative predictive value and AUC of 68Ga-PSMA-11 PET/CT in diagnosing TT were 0.96, 0.97, 0.97, 0.94, 0.97, and 0.97 (95%CI 0.93-0.99) respectively, and 0.91, 0.89, 0.90, 0.94, 0.85, and 0.90 (95%CI 0.79-0.97) in distinguishing early vs advanced TT. The maximum standardized uptake values (SUVmax) for TT was significantly higher than that of the primary tumor lesion (17.65±7.27 vs. 14.04±5.98, P=0.037) and varied significantly among different Mayo levels (P=0.001). The TT length and diameter showed a positive correlation with SUVmax (both P<0.01). Elevated neutrophil counts, neutrophil-to-lymphocyte ratio, and interleukin-6 (IL-6) levels, along with decreased SUVmax, were associated with poor therapeutic efficacy (all P<0.05). Among them, SUVmax for TT was more effective than others with an AUC of 0.75 (95%CI 0.56-0.89).