Delineating biochemical failure with (68)Ga-PSMA-PET following definitive external beam radiation treatment for prostate cancer

We investigated the role of (68)Ga-PSMA-PET (PSMA) to determine the location of disease recurrence in those with a rising PSA following definitive external beam radiation treatment (EBRT).

538men were treated with image guided EBRT to a dose of 78 or 82Gy between 2007 and 2014. Patients at least 24months post EBRT with biochemical failure (nadir+2) underwent PSMA scanning. Local recurrence (LR) was defined as increased uptake within the prostate or seminal vesicles. Distant disease included lymph node (LN), bone or visceral metastases.

419men formed the study cohort. Median follow-up was 50months, 70 patients (17%) had biochemical failure (BF), 13 of whom have died. Of the 57 survivors, 5 had metastases detected on conventional scans; 2 were lost to follow up. 48men (of 50 candidates) underwent PSMA; in all cases, the PSMA was unequivocally positive. Of the 48 positive scans, 25 patients (52%) failed beyond the prostate - 5 in bones, 16LN, 3 in both, and 1 in the lungs. Fifteen men (31%) failed within the gland and in either LN (11), bones (3), or both (1). Eight (17%) had an isolated LR, which represents 2% of patients managed with definitive EBRT and followed for at least 2years.

PSMA was positive in all patients with BF. Site of failure following dose-escalated EBRT was generally distant. Isolated LR (on PSMA) occurred in only 8 of 419 patients post-EBRT.

Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology. 2016 Dec 28 [Epub ahead of print]

George Hruby, Thomas Eade, Andrew Kneebone, Louise Emmett, Lesley Guo, Bao Ho, Ed Hsiao, Geoff Schembri, Julia Hunter, Carol Kwong

Department of Radiation Oncology, Royal North Shore Hospital, Australia; University of Sydney, Sydney, Australia; Genesis Cancer Care, Sydney, Australia. Electronic address: ., Department of Radiation Oncology, Royal North Shore Hospital, Australia; University of Sydney, Sydney, Australia; Genesis Cancer Care, Sydney, Australia., University of New South Wales, Sydney, Australia., Department of Radiation Oncology, Royal North Shore Hospital, Australia., Department of Nuclear Medicine, St Vincent's Hospital, Australia; University of New South Wales, Sydney, Australia., Department of Nuclear Medicine and PET, Royal North Shore Hospital, Australia.