How would x-rays and chemotherapy affect male fertility?

Direct and indirect : X-rays and chemotherapeutic drugs can effect the dividing spermatozoa (sperm cells) in the semen, as well as damage the hormonal (testosterone) production of the testicle. Of course this would depend on the exact drugs and doses, and the dose and location of the x-rays.

Dose-dependent: Regardless of dose, all male patients even considering fathering children in the future should ask about fertility preservation (such as sperm cryopreservation) before any treatment with radiation or chemotherapy. This is an extremely important point that all patients and multi-disciplinary physician teams should be proactive about so that fertility options are explored prior to treatment.