The role of hormone therapy and chemotherapy in oligometastatic prostate cancer

Oligometastatic disease was proposed by Hellman and Weichselbaum in 1995 as an intermediate tumour state between localised lesions and widespread metastases, characterised by the limited number and size of metastases in specific organs such as lung, liver, bone or even brain. The oligometastatic state has increasingly been recognised as a unique clinical state during which local ablative treatment can be effective in several types of cancer, including prostate cancer. However, the role of systemic therapy, such as hormone therapy and chemotherapy, is not yet well known. Some promising data for local ablative therapy have emerged, but it remains unclear whether local therapy can eliminate the need for, androgen-deprivation therapy (ADT), or reduce the required duration. In addition, several randomised phase III trials have demonstrated survival benefits from the addition of docetaxel or abiraterone to ADT in patients with metastatic hormone-sensitive prostate cancer. These findings suggest that such aggressive treatments may improve clinical outcomes for patients with oligometastatic prostate cancer. However, the efficacy of these treatments may depend on the volume of metastases, with higher efficacy for high-volume disease. Therefore, further investigation including stratification by disease volume is warranted. This review will discuss the current evidence and controversies surrounding the role of systemic therapy in patients with oligometastatic prostate cancer.