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Defining Oligometastatic Hormone Sensitive Prostate Cancer and Clinically Significant Outcomes: Implications on Clinical Trials? - Beyond the Abstract

The benefit from the treatment of hormone-sensitive oligometastatic prostate cancer still remains unknown. There are multiple publications looking into such therapy that has grown significantly in the past 6 years, but unfortunately, we are facing a variety of definitions not only of what is considered “oligometastatic prostate cancer”, but also there is a variety of outcomes that difficult the comparison of the results among the different publications.1,2 To be more specific, regarding the definition of oligometastatic prostate cancer, there are discrepancies regarding the number of lesions, location of the lesions, type of imaging studies used to detect the lesions, among others.1, 3-8 When we talk about outcomes, some consider PSA response, time to start androgen deprivation therapy, disease-free survival, among others, in order to define a measurable outcome.1, 5, 9-12 Considering the previous, we felt a need to try to define the current practice among Urologists and gathered information of what would be considered a true clinical benefit for their patients, what outcomes would make it “worthwhile” to recommend a treatment for oligometastatic prostate cancer.


We designed a brief questionnaire and sent it to the members of the Society of Urologic Oncology. We received a total of 119 responses, mostly staff with a significant number of patients with prostate cancer in their practice. Despite the growing literature supporting the use of different PET-CT modalities, the great majority of the respondents did not recommend the use of such imaging for the definition of oligometastatic prostate cancer. Perhaps this is because of availability since such studies are not as widely available as conventional imaging (CT, bone scan, or even MRI). When asked about what would be considered a significant clinical benefit for their patients, most of the physicians considered that a “curing rate” beyond 10% would be a good outcome and a delay in the start of androgen deprivation therapy 1 year or more. Using the obtained answers, we modeled a sample size calculation for a hypothetical clinical trial that could serve for the design of future studies in this controversial stage of prostate cancer.

More studies are required to know if the benefit offered by the treatment of oligometastatic prostate cancer is clinically significant, but perhaps before we are able to do that, we should try to focus on unifying the definitions of the actual stage of the disease, as well as the desired outcomes.

Written by: Jaime O. Herrera-Caceres, MD, Division of Urology, Department of Surgical Oncology, University of Toronto and University Health Network, Toronto, Canada.

References:

  1. Saluja R, Cheung P, Zukotynski K, Emmenegger U. Disease volume and distribution as drivers of treatment decisions in metastatic prostate cancer: From chemohormonal therapy to stereotactic ablative radiotherapy of oligometastases. Urol Oncol. 2016;34(5):225-32.
  2. Al-Shafa F, Arifin AJ, Rodrigues GB, Palma DA, Louie AV. A Review of Ongoing Trials of Stereotactic Ablative Radiotherapy for Oligometastatic Cancers: Where Will the Evidence Lead? Front Oncol. 2019;9:543.
  3. Triggiani L, Alongi F, Buglione M, Detti B, Santoni R, Bruni A, et al. Efficacy of stereotactic body radiotherapy in oligorecurrent and in oligoprogressive prostate cancer: new evidence from a multicentric study. Br J Cancer. 2017;116(12):1520-5.
  4. Franzese C, Di Brina L, D'Agostino G, Franceschini D, Comito T, De Rose F, et al. Predictive factors for survival outcomes of oligometastatic prostate cancer patients treated with metastases-directed therapy: a recursive partitioning-based analysis. J Cancer Res Clin Oncol. 2019;145(10):2469-79.
  5. Bouman-Wammes EW, van Dodewaard-De Jong JM, Dahele M, Cysouw MCF, Hoekstra OS, van Moorselaar RJA, et al. Benefits of Using Stereotactic Body Radiotherapy in Patients With Metachronous Oligometastases of Hormone-Sensitive Prostate Cancer Detected by [18F]fluoromethylcholine PET/CT. Clin Genitourin Cancer. 2017;15(5):e773-e82.
  6. D'Angelillo RM, Francolini G, Ingrosso G, Ravo V, Triggiani L, Magli A, et al. Consensus statements on ablative radiotherapy for oligometastatic prostate cancer: A position paper of Italian Association of Radiotherapy and Clinical Oncology (AIRO). Crit Rev Oncol Hematol. 2019;138:24-8.
  7. Ong WL, Koh TL, Lim Joon D, Chao M, Farrugia B, Lau E, et al. Prostate-specific membrane antigen-positron emission tomography/computed tomography (PSMA-PET/CT)-guided stereotactic ablative body radiotherapy for oligometastatic prostate cancer: a single-institution experience and review of the published literature. BJU Int. 2019;124 Suppl 1:19-30.
  8. Siva S, Bressel M, Murphy DG, Shaw M, Chander S, Violet J, et al. Stereotactic Abative Body Radiotherapy (SABR) for Oligometastatic Prostate Cancer: A Prospective Clinical Trial. Eur Urol. 2018;74(4):455-62.
  9. Deek MP, Yu C, Phillips R, Song DY, Deville C, Greco S, et al. Radiation Therapy in the Definitive Management of Oligometastatic Prostate Cancer: The Johns Hopkins Experience. Int J Radiat Oncol Biol Phys. 2019;105(5):948-56.
  10. Ost P, Jereczek-Fossa BA, As NV, Zilli T, Muacevic A, Olivier K, et al. Progression-free Survival Following Stereotactic Body Radiotherapy for Oligometastatic Prostate Cancer Treatment-naive Recurrence: A Multi-institutional Analysis. Eur Urol. 2016;69(1):9-12.
  11. Ost P, Reynders D, Decaestecker K, Fonteyne V, Lumen N, De Bruycker A, et al. Surveillance or Metastasis-Directed Therapy for Oligometastatic Prostate Cancer Recurrence: A Prospective, Randomized, Multicenter Phase II Trial. J Clin Oncol. 2018;36(5):446-53.
  12. Palma DA, Olson R, Harrow S, Gaede S, Louie AV, Haasbeek C, 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. Lancet. 2019;393(10185):2051-8.

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