Predictive Value of Quantitative ADC, SUVmax, and the SUVmax/ADC Ratio for Biological Behavior and Prognosis in High-Risk Prostate Cancer.

Background/

Objectives

To investigate the importance of ADC, SUVmax, and SUVmax/ADC values in the prognosis and biological behavior of prostate cancer.

Methods

In this retrospective study, ADC measurements in diffusion MRI were made by two radiologists by correlating the lesions with the highest SUVmax value from Ga-68 PSMA PET/CT examinations of 81 patients with prostate cancer. The quantitative values were compared with histopathological grade, presence of perineural invasion, and lymph node and bone metastasis.

Results

For D'Amico high-risk patients, a statistically significant difference among the ADC, SUVmax, and SUVmax/ADC measurements was reported (p < 0.001). Cut-off values were defined as 0.52 (×10-3 mm2/s) for ADC, 9.73 for SUVmax, and 20.28 for the SUVmax/ADC ratio (AUC = 0.887, 0.747, 0.817, respectively) for the high-risk categories. The Youden indices were 0.643, 0.405, and 0.437, respectively. In logistic regression, the SUVmax/ADC ratio was a significant predictor of the high-risk group (AUC = 0.844, p = 0.002), demonstrating superior performance to a model with individual ADC and SUVmax values (AUC = 0.796, p = 0.006). For the advanced-grade group, the SUVmax and SUVmax/ADC ratios differed significantly (p < 0.001). The CAPRA score showed significant correlations with all imaging biomarkers: negatively with ADC (rho = -0.456, p < 0.001) and positively with SUVmax (rho = 0.359, p = 0.001) and the SUVmax/ADC ratio (rho = 0.441, p < 0.001). The presence of perineural invasion had no significant correlation with any of the variables (p > 0.05). The presence of bone metastases and PSA and free PSA levels differed significantly (p = 0.003, p = 0.001, respectively). In the presence of lymph node metastasis, SUVmax and SUVmax/ADC ratios were found to be significant (p = 0.019, p = 0.01, respectively). In the survival (OS) analysis, a low ADC value was found to be associated with shorter survival (median OS: 61 vs. 106 months).

Conclusions

Among advanced-grade and high-risk prostate cancer patients, ADC, SUVmax, and SUVmax/ADC values can be employed as alternative prognostic factors for predicting the biological behavior of the disease.