**6.1 Impact of RT on fertility in males with WT**

Early reports of small numbers of male survivors of WT identified primary gonadal failure following 15–30 Gy flank or WART at 0.5–4 years of age [31] as well as reduced gonadal volume and sperm production after 2.7–9.8 Gy testicular dose after WART [32]. Of note, these findings were attributed to RT as chemotherapy did not show any such effects. An analysis of over 6000 male childhood cancer survivors, of which 429 had WT, revealed RT >7.5 Gy to the testes significantly reduced the ability to father children compared to survivors with no radiation exposure [33].
