Erectile dysfunction can be a side effect of prostate cancer treatment, but depending upon the treatment (surgery or radiation), the onset and quality of symptoms may be different. ED after surgery may stem more from nerve damage, and symptoms may appear soon after surgery.
ED from radiation treatments may not become symptomatic until years after completion of treatment, and the circulation to the penis is thought to be impaired, as opposed to the nerves.
Other than medications, vacuum device therapy is one option that aims to improve circulation to the penis. When used per a specific regimen, this method can prove to have some long-term benefits in over half the men who use it. Your physician can refer you to a penile rehabilitation specialist to explore this option and this may be covered by insurance in some cases.