What risk, if any, do you quote for erectile dysfunction in a young male being treated for a lumbosacral ependymoma?

I have not been quoting a specific risk of ED in spinal ependymoma patients. ED is common with advancing age and is often multifactorial. In ependymoma, prior spine surgery, the disease itself, concurrent medication, concurrent health issues, and the psychological impact of a cancer diagnosis are, for me, more likely culprits than radiotherapy. That said, a minima, ED would be included in any explanation of a small risk of radiculopathy (or myelopathy) that may be pertinent when higher doses or re-irradiation are used.