Purpose:
For high-risk prostate cancer, standard treatment options include radical prostatectomy (RP) or radiotherapy plus androgen deprivation therapy (ADT). Despite definitive therapy, many patients will have disease recurrence. Imaging has the potential to better define characteristics of response and resistance. In this study, we evaluated prostate multiparametric MRI (mpMRI) before and after neoadjuvant enzalutamide plus ADT.
Patients and Methods:
Men with localized intermediate- or high-risk prostate cancer underwent a baseline mpMRI and mpMRI-targeted biopsy followed by a second mpMRI after 6 months of enzalutamide and ADT prior to RP. Specimens were sectioned in the same plane as mpMRI using patient-specific 3D-printed molds to permit mpMRI-targeted biopsies to be compared with the same lesion from the RP. Specimens were analyzed for imaging and histologic correlates of response.
Results:
Of 39 patients enrolled, 36 completed imaging and RP. Most patients (92%) had high-risk disease. Fifty-eight lesions were detected on baseline mpMRI, of which 40 (69%) remained measurable at 6-month follow-up imaging. Fifty-five of 59 lesions (93%) demonstrated >50% volume reduction on posttreatment mpMRI. Three of 59 lesions (5%) demonstrated growth in size at follow-up imaging, with two lesions increasing more than 3-fold in volume. On whole-mount pathology, 15 patients demonstrated minimal residual disease (MRD) of <0.05 cc or pathologic complete response. Low initial mpMRI relative tumor burden was most predictive of MRD on final pathology.
Conclusions:
Low relative lesion volume at baseline mpMRI was predictive of pathologic response. A subset of patients had limited response. Selection of patients based on these metrics may improve outcomes in high-risk disease.
Localized prostate cancer is distinctively characterized by intratumoral heterogeneity, and tumors with more complex evolutionary paths display more aggressive characteristics. In clinical trials of intense neoadjuvant androgen deprivation therapy (inADT), patients with complete or near-complete responses experience durable remissions. However, the molecular characteristics distinguishing exceptional responders and nonresponders at baseline have not been established. Here, we present the integrated histologic and genomic analysis of pre-treatment baseline tissue from our recent Phase 2 clinical study of inADT. Multiregion sampling demonstrated that patients with incomplete and nonresponding tumors demonstrate greater tumor diversity as estimated by phylogenetic tree reconstruction from DNA sequencing and automated analysis of immunohistochemical stains. Development of a four-factor binary model to predict poor response correlated with increased genomic diversity in our 37-patient cohort and a validation cohort of 188 Gleason score 8-10 prostate cancers. Together, these findings demonstrate that even in the primary setting, more highly evolved tumors have increased fitness to resist therapy.
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