National Cancer Institute, Bethesda, MD
Adam G. Sowalsky , Scott Wilkinson , Huihui Ye , Stephanie Harmon , Baris Turkbey , Nicole Carrabba , Rayann Atway , Guinevere Chun , David James VanderWeele , Fatima Karzai , Ravi Amrit Madan , Peter A. Pinto , Peter L. Choyke , William L. Dahut
Background: AR directed therapies are standard of care for metastatic prostate cancer, and their use for high-risk localized disease may improve survival. Previous trials showed that suppression of AR activity resulting in greater pathologic responses improved survival rates. However, the underlying biology and molecular features of exceptionally responding tumors remain unknown. Methods: Men with locally advanced prostate cancer (median Gleason score 8, median PSA 9.58 ng/dl) received mpMRI and MRI/US-fusion targeted biopsies at baseline. Patients received 6 months of ADT plus enzalutamide, then received a second mpMRI, and underwent radical prostatectomy. RP specimens were whole mounted in the same plane as MRI. The location of each tumor on biopsy was mapped to prostatectomy specimens using pathologic and imaging hallmarks. FFPE sections of baseline and post-treatment tumor were stained, laser capture microdissected, and analyzed using whole exome sequencing. Amongst nonresponding patients (residual tumor burden > 0.05 cc) comparison of pre- and post-treatment tumor specimens identified evolutionary phylogenies over space and time representing intrinsic or clonal selection of pre-existing cells. Amongst responding patients, clonal extinction was confirmed by sequencing and immunostaining of surgical specimens. Results: Gleason score at baseline did not differentiate responding and nonresponding patients. Focal ERG staining in biopsies was absent in 100% of responders and present in 60% of responders. Intraductal carcinoma architecture was also absent in all responding tumors. Focal PTEN loss was observed in all nonresponders at baseline. Responding tumor foci were enriched for deletion of chromosome 6q. Comparison of baseline mpMRI sequences indicated a trend towards lower variance on dynamic contract enhanced (DCE) MR and lower local texture heterogeneity metrics in responding lesions. Conclusions: Response to neoadjuvant intense ADT correlates with distinctive pathologic, molecular, and imaging features that can be observed prior to treatment. Selection of patients based on these parameters may improve overall responses to treatment in subsequent clinical trials. Clinical trial information: NCT02430480
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