Single Dose Radiotherapy (SDRT) With or Without Adjuvant Systemic Therapy for Oligometastatic Prostate Cancer

Overview

The present study aims to optimize the use of systemic therapy relative to local tumor ablation in a prospective randomized clinical trial and to validate the existence and characterize the clinical and pathology phenotype of oligometastatic (OM) prostate cancer (OM-PCa). For local tumor ablation we propose to use the novel non-invasive and highly effective technique of Image-Guided Single Dose Radiotherapy (SDRT), which we showed is capable of conferring long-term local relapse-free rates in ≥ 90% of metastatic PCa lesions. Concomitantly, we will develop, validate and implement a diagnostic algorithm for OM-PCa and functionally characterize Prostate Cancer Stem Cells (pCSCs) from human samples to correlate their molecular phenotypes with tumor response to treatment. The long-term aim is to define the indications, standardization of treatment protocols and outcome for OM-PCa. Response assessment will be via local control, metastasis-free survival and overall survival rates. Cases displaying the clinical OM phenotype, as disclosed via long-term disease remission following tumor ablation, will represent the basis to identify the molecular signatures of OM-PCa. These signatures will be used to develop and validate an algorithm to predict the OM phenotype upfront and define the treatment strategy that may lead to cure.

Since a systemic therapy alone is incapable of permanently ablating metastatic prostate cancer (mPCa) lesions, we have designed this clinical trial to explore whether its combination with radiation ablation of low volume (≤3 detectable lesions) mPCa, using the novel and highly effective single dose radiotherapy (SDRT), will render cure of a subset of currently incurable mPCa, as achievable in other tumors at the so-called oligometastatic (OM) phase of tumor progression. Whether OM-PCa does, in fact, exist and whether it can be cured has never been systematically researched. The recent introduction of advanced diagnostic and therapeutic platforms provide new tools to address the OM paradigm in mPCa. For example, while the identification mPCa lesions is still challenging, 18F-Choline and 68Ga-Prostate Specific Membrane Antigen (PSMA) Positron Emission Tomography with Computed Tomography (PET/CT) are emerging as effective modalities for the identification of low volume metastases with a pooled sensitivity and specificity exceeding 85%. Hence, the focus of this project is to use modern diagnostic and therapeutic approaches to detect and ablate low tumor-load mPCa lesions, hypothesizing that a subset these tumors will be detected and treated at the OM phase, and may be cured. We propose that systematic studies of each tumor phenotype and their correlation with clinical outcomes will yield not only a validation of the existence of OM-PCa, but will also enable the generation of an algorithm that predicts the OM phenotype upfront and optimizes the treatment strategy.