Is it possible to target radiation therapy to treat the prostate but not damage my fertility?

Difficult to do: It would be best to store some sperm before undergoing radiation; while the radiation field is concentrated to limit damage to surrounding structures, the radiation can certainly damage the male reproductive tract.

No: Not by how it's targeted because the whole prostate has to be radiated and this will include nerves that may cause impotence. Even if the nerves work the fluid and semen decrease so the sperm will have a harder time to fertilize unless done artificially. The scatter radiation may also damage the testes and permanently effect the sperm. Despite all this you may remain fertile.

Probably: Since prostate cancer usually occurs in patients in their 50-90 years of age, having babies is not the first issue. However, radiotherapy decreases seminal fluid, effects erectile function in some, but younger patients enjoying an active sexual life oftern continue. One needs to check sperm counts before and after, refrain from procreativity for a fe months. Sperm aer made in the testes.