There are two second-line GnRH antagonists for patients with locally advanced or high-risk prostate cancer, degarelix (Firmagon®) and abarelix (Plenaxis®), although the latter has been restricted to patients with no alternative therapy because of associated severe allergic reactions (Table 1) [48, 49], where 3 of the 81 (3.7 %) patients had immediate-onset histamine surges and systemic allergic reactions upon treatment [24, 50]. This evidence concerns the gene GNRH1 and prostate cancer.