CAROPRESE, MARA (2024) Oligoprogressive metastatic prostate cancer: role of stereotactic ablative radiotherapy. [Tesi di dottorato]

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Abstract

In patients with oligoprogressive prostate cancer, because of fewer efficacious options available in later lines of therapy, there is a considerable interest in delay the switch to the next treatment line by stereotactic ablative radiotherapy (SABR) targeted at metastatic sites. The benefit has not yet been conclusively proven. This monocentric retrospective study investigated the role of SABR in this patient setting. From April 2018 to December 2023, 14 patients affected by oligoprogressive prostate cancer were treated with SBRT targeting the nodal or bone sites of progression while maintaining the ongoing systemic therapy. Four patients were receiving a third line of systemic therapy, four a second line and six a first line; three patients were undergoing single-agent ADT (Androgen Deprivation Therapy). All patients were evaluated with a pre-treatment 68Ga-PSMA-11 or 18F-fluorocholine PET/CT, which demonstrated low volume disease. All the active sites were treated with SBRT in one (15–24 Gy) or three (21–27 Gy) fractions, except for one patient, who was treated in five fractions (35 Gy). PSA serum levels were tested at baseline, and at least every three months after RT; all patients underwent a post-treatment 68Ga-PSMA-11 or 18F-fluorocholine PET/CT. The evaluated endpoints were PSA response, defined as a post-treatment decrease >50% from baseline measured within 6 months, time to next-line systemic treatment (NEST), local control (LC), biochemical progression-free survival (bPFS), radiological progression-free survival (rPFS), freedom from polymetastatic progression (FPP), and overall survival (OS). Twenty-five lesions were treated (seven nodal and eighteen bone). At a median follow-up of 25 months (10–78), 12 of the 14 patients had a PSA response; all patients had local control of the treated sites. A total of eight patients switched to a next-line systemic treatment, with an estimated median NEST of 18 months. Seven patients had polymetastatic progression with an estimated FPP median time of 19 months. Two patients died during the follow-up period; three-years overall survival was 73.3%. The SBRT-related toxicity was negligible. Our data support the use of SBRT targeting the sites of oligoprogressive disease before moving to a subsequent line of systemic treatment in patients with metastatic prostate cancer. Further prospective studies to assess the impact on overall survival should be performed.

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