Are all gonadotrophin-releasing hormone agonists equivalent for the treatment of prostate cancer? A systematic review.

To review direct comparative studies of the gonadotrophin-releasing hormone (GnRH) agonists goserelin, triptorelin, and leuprorelin for the treatment of prostate cancer, and identify whether there are meaningful clinical differences between these agents. In June 2017, the following searches were performed independently by two reviewers in PubMed: (i) 'prostate cancer' and 'triptorelin' and 'leuprorelin', (ii) 'prostate cancer' and 'triptorelin' and 'goserelin', and (iii) 'prostate cancer' and 'goserelin' and 'leuprorelin', without time restriction. Duplicates were deleted. Relevant conference abstracts were also screened. A total of 16 direct comparative trials were identified: 12 reported on efficacy outcomes, four on safety/tolerability, and five on the convenience of administration/user perceptions. These studies are restricted in terms of patient numbers, formulations assessed, and endpoints measured; none were adequately powered for survival outcome measures. Studies reporting on efficacy endpoints did not show major differences in the ability of these GnRH agonists to reduce levels of testosterone or prostate-specific antigen. Some studies suggest differences in short- or long-term testosterone control, the rate of injection site adverse events, and patient/healthcare professional perceptions, but definitive conclusions cannot be drawn from the existing evidence. Few direct comparative trials of GnRH agonists have been conducted. Whilst GnRH agonists provide a similar castration effect, there is not enough evidence to show that GnRH agonists are equivalent.