Oral/metronomic cyclophosphamide-based chemotherapy as option for patients with castration-refractory prostate cancer: review of the literature

Abstract

Purpose: Castration-refractory prostate cancer remains a therapeutic challenge even after introduction of docetaxel as first-line treatment. Castration-refractory prostate cancer cannot be cured by any available therapeutic option, and chemotherapy still needs to be considered palliative. The survival benefit is modest, and treating physicians are searching for alternative treatment options. Despite new drugs currently under investigation, some conventional and well known chemotherapeutic drugs are experiencing a renaissance. The development of anti-angiogenic approaches in cancer treatment has led to the development of metronomic dosing of conventional chemotherapeutic drugs including cyclophosphamide. The intention of this review is to evaluate the efficacy and toxicity of oral/metronomic cyclophosphamide in the treatment of patients with castration-refractory prostate cancer.

Materials and methods: A comprehensive literature search was performed in different databases using various key words. Relevant articles and references between 1962 and 2010 were reviewed and analyzed for data regarding the association between oral cyclophosphamide treatment and prostate cancer.

Results: Oral cyclophosphamide is active in the treatment for castration-refractory prostate cancer even in patients treated with previous chemotherapy including docetaxel. It yields symptomatic and objective remissions. The side effects are usually grade 1-2 and easy to manage. Grade three to four side effects are less common.

Conclusions: Oral cyclophosphamide treatment for patients with castration-refractory prostate cancer deserves more attention and validation, and warrants further testing of various treatment combinations. Given the fact that castration-refractory prostate cancer includes an extremely heterogeneous group of patients with variability of tumor growth rates, the combination of cyclophosphamide with other active agents such as angiogenesis inhibitors and immunomodulatory compounds need to be explored.