The pathology report from the original biopsy will indicate whether or not the doctor reading the slide believes that there was invasion of the tumor beyond the prostate. However, the ONLY way anyone "knows" if there has been tumor penetration beyond the prostate is to have surgery. Following surgery there will be a deep pathology of the prostate and it will indicate detectable invasion or not beyond the prostate. Even this post-op report cannot guarantee there was no invasion, but the odds are very high that the cancer has been fully removed if the margins of the prostate are negative for cancer.
When you have radiation therapy as opposed to surgery, the prostate is effectively killed and the cancer along with it. This is done by the doctor carefully estimating the extend of the tumor and protecting the body as much as possible outside of the prostate and focusing the radiation on the prostate and tumor. Other's can "chime in" here, since I'm not an expert in the radiation therapy.
You're asking great questions, livingthedream. Please continue to stay close and be engaged.
Our thoughts and prayers go out to you and your husband.