Correlation Between Quantitative PSMA PET Parameters and Clinical Risk Factors in Non-Metastatic Primary Prostate Cancer Patients

Abstract

Background: PSMA PET is frequently used for staging of prostate cancer patients. Furthermore, there is increasing interest to use PET information for personalized local treatment approaches in surgery and radiotherapy, especially for focal treatment strategies. However, it is not well established which quantitative imaging parameters show highest correlation with clinical and histological tumor aggressiveness.

Methods: This is a retrospective analysis of 135 consecutive patients with non-metastatic prostate cancer and PSMA PET before any treatment. Clinical risk parameters (PSA values, Gleason score and D'Amico risk group) were correlated with quantitative PET parameters maximum standardized uptake value (SUV_max), mean SUV (SUV_mean), tumor asphericity (ASP) and PSMA tumor volume (PSMA-TV).

Results: Most of the investigated imaging parameters were highly correlated with each other (correlation coefficients between 0.20 and 0.95). A low to moderate, however significant, correlation of imaging parameters with PSA values (0.19 to 0.45) and with Gleason scores (0.17 to 0.31) was observed for all parameters except ASP which did not show a significant correlation with Gleason score. Receiver operating characteristics for the detection of D'Amico high-risk patients showed poor to fair sensitivity and specificity for all investigated quantitative PSMA PET parameters (Areas under the curve (AUC) between 0.63 and 0.73). Comparison of AUC between quantitative PET parameters by DeLong test showed significant superiority of SUV_max compared to SUV_mean for the detection of high-risk patients. None of the investigated imaging parameters significantly outperformed SUV_max.

Conclusion: Our data confirm prior publications with lower number of patients that reported moderate correlations of PSMA PET parameters with clinical risk factors. With the important limitation that Gleason scores were only biopsy-derived in this study, there is no indication that the investigated additional parameters deliver superior information compared to SUV_max.

Keywords: PSMA; positron emission tomography; primary prostate cancer; prostate specific membrane antigen; quantitative PET parameters.

Figure 1

Correlation between serum prostate-specific antigen (PSA) values and quantitative PSMA-PET parameters. (A) PSMA-derived tumor volume (PSMA-TV), (B) Maximum standardized uptake value (SUVmax), (C) Mean standardized uptake value (SUVmean) and (D) Tumor asphericity (ASP). PSA values are plotted on a logarithmic scale.

Figure 2

Correlation between Gleason scores obtained by biopsy before imaging and quantitative PSMA-PET parameters. (A) PSMA-derived tumor volume (PSMA-TV), (B) Maximum standardized uptake value (SUVmax), (C) Mean standardized uptake value (SUVmean) and (D) Tumor asphericity (ASP).

Figure 3

Boxplots showing the distribution of quantitative PET parameters for each Gleason score. (A) PSMA-derived tumor volume (PSMA-TV), (B) Maximum standardized uptake value (SUVmax), (C) Mean standardized uptake value (SUVmean) and (D) Tumor asphericity (ASP). Outliers are plotted as points (< 3 * interquartile range) or asterisks (> 3 * interquartile range).

Figure 4

Receiver operating characteristics (ROC) curves to detect high-risk prostate cancer using quantitative PSMA-PET parameters. (A) PSMA-derived tumor volume (PSMA-TV), (B) Maximum standardized uptake value (SUVmax), (C) Mean standardized uptake value (SUVmean) and (D) Tumor asphericity (ASP).