How do you counsel a young man receiving EBRT as part of TNT for rectal cancer about risk of infertility?

I counsel male patients that, although the testes are outside the target dose volume, they will receive enough radiation that it could, at least temporarily, impair their ability to conceive. I offer to refer them for sperm banking prior to starting treatment.

I agree with Dr. @Dr. First Last answer. Another option is to consider the use of a testicular shielding device. Many studies for the treatment of testicular seminoma to the 40 Gy showed about 0.3% of the prescribed dose to the testis, which can maintain fertility (Singhal et al., PMID 24841161).