Management of Oligoprogressive Castration Resistant Prostate Cancer (PCS X)

Metastases-directed therapy with stereotactic body radiation therapy (SBRT) is emerging as a new treatment option for solid tumor patients with a limited number of metastases (\< 5) at the time of recurrence/progression, so called oligoprogression therapy. As such, oligoprogression is defined as prostate cancer patients with castration resistance and no metastases (M0CRPC) who are receiving ADT and new generation hormonal therapy (enzalutamide, apalutamide or darolutamide) as standard of care, and who are then progressing to oligometastases. The new generation hormonal therapy used in this study will be darolutamide (ODM-201). The rationale behind this approach has been to delay the start of palliative systemic therapies that are most often toxic and associated with a negative impact on patient's quality of life, as well as being more costly. However, to date, there are no prospective published data or ongoing studies that are looking into non metastatic castration resistant prostate cancer (M0CRPC) patients who progress to oligometastases (oligoprogression). To this end, we are proposing this pilot phase II trial to assess the impact of SBRT on radiological progression-free survival (RPFS) of M0CRPC patients who are receiving darolutamide and progress to oligometastatic disease (oligoprogression). Prostate cancer patients with castration resistance and no metastases (M0CRPC) diagnosed by bone scan and CT scan or MRI will be recruited in this phase II and initiate darolutamide while continuing on ADT (Part 1 of the study), if not receiving darolutamide prior to study entry already. Patients who then progress to wide spread metastases or metastases situated at locations not amenable to ablative therapy will be excluded and treated with second line therapy as per the treating physician. Patients with oligoprogression (\< 5 mets) and amenable to ablative therapy will be then treated with SBRT or surgery as an ablative therapy if SBRT is not feasible (Part 2 of the study). All patients will continue to receive non-interrupted LHRH agonist, PSA testing every 6-12 weeks and re-imaging every 6 months. Imaging will also be repeated at the appearance of symptoms or at PSA progression, whichever occurs first and this schedule continues until disease progression. This is the first pilot phase II trial assessing the response of SBRT layered on darolutamide on RPFS and deferring palliative second line systemic therapy in M0CRPC with oligoprogression. This phase II will consist of 66 M0CRPC patients treated with darolutamide, of which we anticipate 48 will be eligible for SBRT.