Erectile dysfunction or impotence is a common side effect for men who get treatment for prostrate cancer. The problem before was 
that there was no study to give an insight into what chances an individual had of getting impotent after getting different types of treatment for prostrate problems; which include surgery and radiation.
Now a new study recently published in the Journal of The American Medical Association has come up with formulas that will help doctors to get a fair idea of the risk a patient has of suffering from impotence after taking the different types of treatment for prostrate cancer. The researchers of this study were able to correctly predict the chances of post treatment potency in 77% of the men who had surgery and 90% of the men whose prostate was treated with radiation.
This study and the formula that it provides to calculate the risk of impotency for prostrate patients should only be taking as estimate of the chances of ED for a particular type of treatment and used only after the patient has decided upon the type of treatment. It should not be used to choose between surgery and radiation treatment just because one may have a lower risk of post treatment impotency than the other, as the more important thing is to have the right treatment for the individual to treat prostrate cancer rather than worry about ED.
What this helps is to prepare the patient to come to terms with the risks and helps him prepare for any type of sexual dysfunction after the prostrate cancer treatment. There are various treatments available to help regain proper sexual function for such men which varies from medication to penile implants depending on the severity of the problem.
You can read more about this study here.