Infiltrative growth pattern of prostate cancer is associated with lower uptake on PSMA PET and reduced diffusion restriction on mpMRI

Purpose Recently, a significant association was shown between novel growth patterns on histopathology of prostate cancer (PCa) and prostate-specific membrane antigen (PSMA) uptake on [ 68 Ga]PSMA-PET. It is the aim of this study to evaluate the association between these growth patterns and ADC (mm 2 /1000 s) values in comparison to [ 68 Ga]PSMA uptake on PET/MRI. Methods We retrospectively evaluated patients who underwent [ 68 Ga]PSMA PET/MRI for staging or biopsy guidance, followed by radical prostatectomy at our institution between 07/2016 and 01/2020. The dominant lesion per patient was selected based on histopathology and correlated to PET/MRI in a multidisciplinary meeting, and quantified using SUV max for PSMA uptake and ADC mean for diffusion restriction. PCa growth pattern was classified as expansive (EXP) or infiltrative (INF) according to its properties of forming a tumoral mass or infiltrating diffusely between benign glands by two independent pathologists. Furthermore, the corresponding WHO2016 ISUP tumor grade was evaluated. The t test was used to compare means, Pearson’s test for categorical correlation, Cohen’s kappa test for interrater agreement, and ROC curve to determine the best cutoff. Results Sixty-two patients were included (mean PSA 11.7 ± 12.5). The interrater agreement between both pathologists was almost perfect with κ = 0.81. While 25 lesions had an EXP-growth with an ADC mean of 0.777 ± 0.109, 37 showed an INF-growth with a significantly higher ADC mean of 1.079 ± 0.262 ( p < 0.001). We also observed a significant difference regarding PSMA SUV max for the EXP-growth (19.2 ± 10.9) versus the INF-growth (9.4 ± 6.2, p < 0.001). Within the lesions encompassing the EXP- or the INF-growth, no significant correlation between the ISUP groups and ADC mean could be observed ( p = 0.982 and p = 0.861, respectively). Conclusion PCa with INF-growth showed significantly lower SUV max and higher ADC mean values compared to PCa with EXP-growth. Within the growth groups, ADC mean values were independent from ISUP grading.