(UroToday.com) The 2023 SNMMI annual meeting included a prostate cancer session, featuring a presentation by Dr. Muheon Shin discussing predictive features of 18F-DCFPyL PSMA PET/MRI in high-risk prostate cancer patients treated with neoadjuvant chemohormonal therapy prior to radical prostatectomy. Neoadjuvant chemohormonal therapy followed by cytoreductive radical prostatectomy is a novel and emerging therapeutic approach in patients with newly diagnosed high-risk primary prostate cancer with oligometastatic disease.
Additionally, PSMA PET/MR demonstrates superior sensitivity and specificity in detection of high-risk primary prostate cancer when compared to conventional imaging. However, limited data is available on the utility of PSMA-based PET and mpMRI in the assessment of response to neoadjuvant therapy. As such, the purpose of this study presented by Dr. Shin and colleagues was to investigate PET and MRI imaging features in 18F-DCFPyL PSMA PET/MRI of the prostate and its predictive value for response and disease progression in men with high risk prostate cancer treated with neoadjuvant chemohormonal therapy.
There were 27 men with biopsy-proven, locally advanced, high-risk prostate cancer that were enrolled in this prospective phase II clinical trial. Relevant inclusion criteria included high risk prostate cancer defined as: (i) extracapsular extension (cT3a), or (ii) seminal vesicle involvement (cT3b), or (iii) invasion of adjacent structures (cT4), or (iv) serum PSA >20 ng/mL, (v) or a Gleason score of 8 to 10 and/or (vi) regional lymph node involvement. Inclusion criteria allowed for patients with oligometastatic disease with three or less bone metastases but no visceral metastases. All patients underwent 3 cycles of neoadjuvant chemohormonal therapy followed by radical prostatectomy. Whole body and pelvis PSMA PET/MRI with 3.0T pelvic multiparametric MRI were performed at:
- Baseline: PETMR1
- After neoadjuvant chemohormonal therapy: PETMR2
- 1 year after radical prostatectomy or earlier if there was evidence of biochemical recurrence by elevated PSA level: PETMR3
Qualitative visual and quantitative assessments were performed by an experienced nuclear medicine physician and abdominal radiologist for the PET and MRI, respectively. Visual assessment using a 5-point Likert scale was used in both PSMA PET (PET score) and mpMRI (MRI score). Suspected tumor lesion SUVmax was obtained from the PSMA PET, and diffusion-weighted imaging (DWI), apparent diffusion coefficient (ADC), and dynamic contrast-enhanced (DCE) were obtained from the pelvic mpMRI:
PET and MRI parameters of the detected prostate cancer lesions were represented as mean of all detected lesions, and the lowest and highest values in each patient from PETMR1 and PETMR2. Clinical outcome was defined as biochemical recurrence, defined as any detectable PSA level rising on two consecutive checks 4 weeks apart for non-metastatic patients, and PSA rising over two consecutive checks for oligo-metastatic patients. Cox proportional hazards survival regression analysis was performed on the PET and MRI parameters to assess the association with the progression of the disease. Bivariate analyses of the PETMR1 and PETMR2 time points were also performed.
Among these 27 patients, the mean age was 61 years and mean PSA was 39.6 ng/mL. Clinical follow-up was a median of 855 days (range 114 – 1315), and 18 patients showed biochemical recurrence a mean 378 days (212 ± 140 days) from treatment. In univariate cox regression analysis of PET and MRI parameters, the most statistically significant parameters ranked by p-value was SUVmax, MRI score (visual score) and DWI at PETMR2 for both mean and highest values:
PETMRI1 parameters were found to be statistically significant but less predictive, with top parameters including SUVmax and MRI score mean values, and SUVmax highest values. In bivariate cox regression analysis, the combination of the two top predictive parameter, SUVmax and MRI score mean and highest values were found to be more predictive than either value alone, with mean SUVmax and mean MRI score at PETMR2 (p < 0.0001) and highest SUVmax and highest MRI score at PETMR2 (p = 0.0001):
Kaplan-Meier survival analysis using SUVmax mean value and highest value is as follows:
Scatter plot of the post-chemohormonal therapy SUVmax and MRI score shows clustering of patients with no biochemical recurrence in the low SUVmax and low MRI score quadrant:
Dr. Shin concluded this presentation discussing predictive features of 18F-DCFPyL PSMA PET/MRI in high-risk prostate cancer patients treated with neoadjuvant chemohormonal therapy prior to radical prostatectomy with the following take home messages:
- Visual qualitative and quantitative features extracted from prostate PSMA PET/MRI can be used to assess treatment response and predict progression in this emerging neoadjuvant chemohormonal therapy prostate cancer treatment setting
- Post-chemohormonal therapy imaging is more predictive than pre-chemohormonal therapy
- SUVmax and MRI visual score were the most predictive parameters
- Even great prediction was noted with the combination of SUVmax and MRI score than either component alone
- Validation in larger clinical trials is needed, including correlation with clinical, histopathologic, and genetic parameters
- PSMA PET/MRI may be a promising tool for response assessment in prostate cancer
Presented by: Muheon Shin, MD, University of Wisconsin, Madison, WI
Written by: Zachary Klaassen, MD, MSc – Urologic Oncologist, Associate Professor of Urology, Georgia Cancer Center, Augusta University/Medical College of Georgia, @zklaassen_md on Twitter during the 2023 Society of Nuclear Medicine and Molecular Imaging (SNMMI) Annual Meeting, Chicago, IL, Sat, June 24 – Tues, June 27, 2023.