['• To explore the efficacy and safety of testosterone undecanoate (TU) (Nebido®; Bayer Schering Pharma AG, Berlin, Germany) in patients with bilateral germ cell testicular cancer (GCTC) who have switched androgen substitution from testosterone enanthate (Primoteston Depot®, Bayer Schering Pharma AG).', "• In total, 47 bilaterally orchidectomized GCTC patients were included in a prospective study to monitor serum gonadal hormones, biochemical safety and symptoms of hypogonadism based on the Aging Males' Symptoms scale during TU treatment for a 28-week period.", "• During treatment, serum levels of total (TT) and calculated free testosterone (CFT) increased with simultaneously decreasing levels of FSH and LH. However, considerable variations in median levels of TT and CFT were observed during the study. The highest levels of TT and CFT were observed 1-2 weeks after each injection and the lowest immediately before the second injection. • Insufficient levels of TT (< 8 nmol/L) were observed in 10 patients, with nine of these during the second half of the first treatment cycle. Supernormal levels of TT (> 35 nmol/L) were measured in 28 patients of which 26 occurred at least once during the first 3 weeks of each treatment cycle. • A follow-up review at median 39 months after study start showed a median steady-state injection interval of 10 weeks, with an individual variability of 6-14 weeks. Symptoms according to the Aging Males' Symptoms scale remained unchanged. No severe toxicity was encountered. Only one patient experienced transient elevation of serum alanine transaminase and aspartate transaminase with maximal Common Toxicity Criteria, grade 2."] Does androgen substitution with testosterone undecanoate in survivors of bilateral testicular cancer require individually-adjusted injection intervals?