Novel Insights into the Management of Oligometastatic Prostate Cancer: A Comprehensive Review

Abstract

Context: The current standard of care for metastatic prostate cancer (PCa) is androgen deprivation therapy (ADT) plus either docetaxel or abiraterone. Growing evidence suggests that metastasis-directed therapy (MDT) and/or local therapy targeted to the primary tumour (ie, prostate) may be of benefit in the setting of oligometastatic disease. Several prospective studies are underway; however, until robust evidence is available to guide treatment decisions, physicians are challenged with how best to manage patients with oligometastases.

Objective: This comprehensive review aims to collate the available evidence to date for a role of MDT and/or prostate-targeted therapy in the setting of oligometastatic PCa, as well as discuss ongoing trials in this setting.

Evidence acquisition: We searched PubMed for the combination of "prostate cancer" and "oligometastatic", "oligometastases", "oligometastasis", "solitary metastases", "stereotactic body radiotherapy", "SBRT", "stereotactic ablative radiotherapy", "SABR", "salvage lymphadenectomy", or "metastasectomy" in publications over the last 20yr. We also searched ClinicalTrials.gov to identify relevant ongoing trials.

Evidence synthesis: The studies were divided according to the timing of metastasis into synchronous (ie, detected at the time of primary PCa diagnosis) and metachronous (ie, detected after treatment of the primary tumour), and according to treatment modality into MDT (including salvage lymph node dissection [sLND]) and prostate-targeted treatment. For MDT of synchronous/metachronous metastases, we included 16 completed studies and 11 ongoing prospective studies. In the case of sLND for nodal-only recurrence after primary treatment with curative intent, we included 11 completed studies. Finally, for prostate-targeted treatment of synchronous metastatic PCa, we included 25 completed studies and 11 ongoing prospective studies. In selected patients with oligorecurrent disease, early detection and aggressive treatment of metastatic lesions (surgery or radiotherapy) appears to be a feasible strategy and may delay the use of systemic therapies. MDT is a promising option in oligometastatic PCa patients, but more robust data are needed. In the setting of synchronous oligometastatic disease, aggressive cytoreductive treatment needs further data to confirm the benefits.

Conclusions: In this review, we provide a comprehensive overview of the current literature on the treatment of patients with oligometastatic PCa. The data suggest that although ADT plus either docetaxel or abiraterone remains the mainstay of treatment for mPCa, in oligometastatic PCa, improved outcomes may be achieved with metastasis- and prostate-targeted therapies. The studies included in this review are mainly retrospective in nature, limiting the strength of the evidence they provide. Prospective studies are ongoing, and their results are eagerly awaited.

Patient summary: We reviewed the treatment of patients with prostate cancer that has spread to five sites or fewer. We conclude that while androgen deprivation plus either docetaxel or abiraterone should remain the standard of care, there is evidence that treatment targeted at the metastases and the primary tumour may improve the outcome for the patient and potentially delay the use of systemic treatment.

Keywords: Metastasis-directed therapy; Oligometastatic; Prostate cancer; Prostate-targeted treatment.