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18F-Fluciclovine Positron Emission Tomography in Men with Biochemical Recurrence of Prostate Cancer After Radical Prostatectomy and Planning to Undergo Salvage Radiotherapy: Results from LOCATE - Beyond the Abstract

Biochemical recurrence after definitive therapy for prostate cancer is often faced by urologic oncologists and radiation oncologists. Historically, these patients may undergo workup with conventional imaging including computed tomography (CT), magnetic resonance imaging (MRI), and/or bone scans. However, these imaging modalities have limited sensitivity at lower prostate-specific antigens (PSA). More recently, advances in prostate cancer-specific positron emission tomography (PET) radiotracers have established new understandings of disease recurrence patterns. One of these radiotracers is 18F-fluciclovine, which is a synthetic amino acid that is preferentially taken up by prostate cancer cells - making it an attractive target as a radiotracer. 18F-Fluciclovine PET scans were FDA-approved for biochemically recurrent prostate cancer in 2016 and incorporated into the National Comprehensive Cancer Network (NCCN) guidelines in 2018.1



The LOCATE trial aimed to assess the impact of fluciclovine PET/CT scan on the treatment decisions of patients with biochemically recurrent prostate cancer after definitive surgery or radiation.2 Andriole et al. found that the majority of men (57%) had one or more positive findings on their PET scan, and 59% of men had changes in their primary treatment plan for recurrence.

In the present subgroup analysis of men who were planned to undergo salvage radiation after radical prostatectomy, we aimed to identify the utility of this modality in making decisions regarding salvage radiotherapy. We found that nearly half (42%) of patients had a positive finding, with 21% having extrapelvic sites suspicious for metastatic disease. Forty-eight percent of patients planned for salvage radiation had a management change after PET scan, with two-thirds of these patients having a change in the overall treatment approach and one-third of these patients having a radiation target change.3

We found that multiple patients had radiation changes that included metastasis-directed therapy for oligometastatic disease. The use of ablative radiation in oligometastatic patients is an emerging area of radiation oncology. Previous trials such as STOMP and ORIOLE have shown that SBRT can be used to delay the use of androgen deprivation therapy (ADT) in patients with oligorecurrent prostate cancer.4,5 Furthermore, the SABR-COMET trial suggested potentially improved survival with metastasis-directed SBRT in oligorecurrent cancers.6 These findings have led to the creation of multiple ongoing Phase II and III trials employing SBRT in the oligometastatic setting of prostate cancer. Examples of this include the PRESTO (NCT04115007) and the PLATON (NCT03784755) trials. In such trials, as in clinical practice, proper patient selection is paramount, and imaging studies such as advanced PET/CT imaging play a key role.

In addition to metastasis-directed therapy, the employment of ADT may also be altered with the use of advanced PET/CT imaging. The studies that cite for the benefit of ADT (RTOG 0534, RTOG 9601, GETUG-AFU 16) were all done prior to the advent of prostate-specific PET/CT scans, with decisions based on clinical characteristics, conventional imaging workup, and PSA alone.7-9 The decision of whether to offer a patient ADT in the salvage radiation setting and the duration of the ADT can be a difficult one, especially in patients with lower PSAs. In our analysis of LOCATE, we found that of the patients who had a change in management approach, 11% of changes included the addition of ADT to salvage RT.

However, providers must be cautious in making changes in management based on PET/CT findings. Although studies such as ours suggest the utility of imaging modalities like 18F-Fluciclovine, the clinical impact of these changes on long-term patient outcomes is unknown. Current trials are ongoing to answer this question (NCT03553602, NCT01666808, NCT02974075, NCT03582774, NCT03762759, NCT03525288). Trials such as this will help guide management in the future.

The role of prostate cancer-specific PET/CT radiotracers is an evolving one, and with further study, will hopefully help physicians to provide the highest quality care to every prostate cancer patient.

Written by: Grant Harmon, MD, Resident of Radiation Oncology, Stritch School of Medicine, Loyola University, Chicago, Illinois, Dennis Chan, MD, Resident of Radiation Oncology, Stritch School of Medicine, Loyola University, Chicago, Illinois, and Abhishek Solanki, MD, Associate Professor, Director of Clinical Research & Quality Medical Director, Department of Radiation Oncology, Stritch School of Medicine, Loyola University, Chicago, Illinois

References:

  1. National Comprehensive Cancer Network. Prostate Cancer (Version 2.2020) https://www.nccn.org/professionals/physician_gls/pdf/prostate.pdf
  2. Andriole, Gerald L., Lale Kostakoglu, Albert Chau, Fenghai Duan, Umar Mahmood, David A. Mankoff, David M. Schuster, and Barry A. Siegel. "The impact of positron emission tomography with 18F-fluciclovine on the treatment of biochemical recurrence of prostate cancer: results from the LOCATE trial." The Journal of urology 201, no. 2 (2019): 322-331.
  3. Solanki, Abhishek A., Bital Savir-Baruch, Stanley L. Liauw, Jeff Michalski, Jonathan D. Tward, Neha Vapiwala, Eugene J. Teoh et al. "18F-Fluciclovine positron emission tomography in men with biochemical recurrence of prostate cancer after radical prostatectomy and planning to undergo salvage radiotherapy: Results from LOCATE." Practical Radiation Oncology (2020).
  4. Ost, Piet, Dries Reynders, Karel Decaestecker, Valérie Fonteyne, Nicolaas Lumen, Aurelie DeBruycker, Bieke Lambert et al. "Surveillance or metastasis-directed therapy for oligometastatic prostate cancer recurrence: A prospective, randomized, multicenter phase II trial." Journal of Clinical Oncology 36, no. 5 (2018): 446-53.
  5. Phillips, Ryan, William Yue Shi, Matthew Deek, Noura Radwan, Su Jin Lim, Emmanuel S. Antonarakis, Steven P. Rowe et al. "Outcomes of observation vs stereotactic ablative radiation for oligometastatic prostate cancer: the ORIOLE phase 2 randomized clinical trial." JAMA oncology 6, no. 5 (2020): 650-659.
  6. Palma, David A., Robert Olson, Stephen Harrow, Stewart Gaede, Alexander V. Louie, Cornelis Haasbeek, Liam Mulroy et al. "Stereotactic ablative radiotherapy versus standard of care palliative treatment in patients with oligometastatic cancers (SABR-COMET): a randomised, phase 2, open-label trial." The Lancet 393, no. 10185 (2019): 2051-2058.
  7. Shipley, William U., Wendy Seiferheld, Himanshu R. Lukka, Pierre P. Major, Niall M. Heney, David J. Grignon, Oliver Sartor et al. "Radiation with or without antiandrogen therapy in recurrent prostate cancer." New England Journal of Medicine 376, no. 5 (2017): 417-428.
  8. Carrie, Christian, Ali Hasbini, Guy de Laroche, Pierre Richaud, Stéphane Guerif, Igor Latorzeff, Stéphane Supiot et al. "Salvage radiotherapy with or without short-term hormone therapy for rising prostate-specific antigen concentration after radical prostatectomy (GETUG-AFU 16): a randomised, multicentre, open-label phase 3 trial." The Lancet Oncology 17, no. 6 (2016): 747-756.
  9. Pollack, A., T. G. Karrison, A. G. Balogh, D. Low, D. W. Bruner, J. S. Wefel, L. G. Gomella et al. "Short term androgen deprivation therapy without or with pelvic lymph node treatment added to prostate bed only salvage radiotherapy: the NRG Oncology/RTOG 0534 SPPORT trial." International Journal of Radiation Oncology• Biology• Physics 102, no. 5 (2018): 1605.
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