Patterns of prostate cancer recurrence after brachytherapy determined by PSMA PET/CT imaging.

The aim of this study was to characterize the patterns of prostate cancer recurrence after brachytherapy (BT) using [18F]DCFPyL PSMA PET/CT imaging.

Patients were selected from an ongoing prospective institutional trial, investigating the utility of [18F]DCFPyL PSMA PET/CT in recurrent prostate cancer (NCTXXXXXXXX). This report included patients who underwent BT (either monotherapy or boost) and experienced a biochemical failure (BF) defined by the Phoenix definition (prostate-specific antigen (PSA) > 2 ng/mL above nadir).

Between March 2017 and April 2020, 670 patients underwent [18F]DCFPyL PSMA PET/CT imaging. 93 of these 670 patients were treated with BT; 73 underwent monotherapy and 20 underwent BT boost (19 LDR and 1 HDR). To report on patterns of recurrence outcomes, 86 patients (median pre-scan PSA 6.0) with a positive [18F]DCFPyL PSMA PET/CT scan and true BF were included. The most common location of relapse was local; 62.8% had a component of local failure (defined as prostate and/or seminal vesicles) and 46.5% had isolated local failure only, with no other sites of involvement. 40.7% of patients had regional failure and 36.0% had metastatic failure. Isolated local recurrence was seen in 54.3% of monotherapy patients vs. only in 12.5% of boost patients. Metastatic failure was seen in 28.6% of monotherapy patients vs. 68.8% of the boost patients. 69.0% of local recurrences were found within the same prostate biopsy sextant involved with tumor at diagnosis and 76.0% of patients with seminal vesicle recurrences had prostate base involvement at diagnosis.

Contrary to previous evidence, our study suggests that in prostate BT patients with biochemical recurrence, the most common site of failure is local for the patients treated with monotherapy, and metastatic for patients treated with combination of external beam radiation and BT boost.

International journal of radiation oncology, biology, physics. 2022 Jan 02 [Epub ahead of print]

Srinivas Raman, Mira Keyes, Justin Oh, Etienne Rousseau, Andra Krauze, Don Wilson, François Bénard

Department of Radiation Oncology, BC Cancer Vancouver, BC, Canada., Department of Radiation Oncology, BC Cancer Vancouver, BC, Canada. Electronic address: ., Functional Imaging Department BC Cancer Vancouver, BC, Canada., Department of Radiation Oncology BC Cancer Surrey, BC, Canada.

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