One of the most common complications of radiation therapy and surgery (prostatectomy) for prostate cancer is erectile dysfunction (ED.) Studies report rates as high as 30-60% of men who undergo these treatments will develop ED as a result of treatment (and higher with hormonal therapy, although often reversible once discontinued.)
Causes of Treatment-Related ED:
There are many factors that can lead to ED after prostate cancer treatment. In the vast majority of cases, ED results from injury to the penile nerves or blood vessels during surgery (i.e. stretching, cutting or burning of nerves during surgery, disruption of blood supply, inflammation associated with surgical trauma, etc.) or after surgery or radiation therapy (i.e. injury to the penile or nerve blood supply.)
Oxygenation of the penis is important in maintaining healthy erections. When the penile blood supply is diminished (through blood vessel and/or nerve injury), permanent scaring (fibrosis) of the penile tissues and narrowing of blood vessels begins to develop. Penile shortening can also develop as a result of tissue fibrosis.
ED related to hormonal therapy (androgen deprivation therapy or “ADT”) is caused primarily from a decrease in testosterone stimulation, leading to loss of libido and penile blood flow. The use of hormonal therapies for prostate cancer do not typically lead to permanent structural changes in the penis, and the associated ED is often reversible when the hormonal therapy is discontinued and testosterone levels normalize.
What is “Penile Rehab?”
Basically, penile rehab (PR) is the maintenance of erectile function by preventing penile fibrosis through various interventions that artificially induce erections.
Studies have demonstrated that the risk of developing ED after prostate surgery or radiation can be reduced with commonly prescribed ED medications started shortly (days-to-weeks) after surgery or during radiation therapy.
- Prostaglandins are a class of medication that increases penile blood flow through relaxing blood vessels in the penis, allowing blood to fill the penis. These medications can either be injected subcutaneously into the base of the penis or through a small dissolvable tablet inserted into the urethral orifice (“MUSE” or medicated urethral system for erection.) In a Cleveland Clinic study, patients were randomized to either MUSE (initiated 3 weeks after surgery and continued for 6 months) or a control (no treatment). The researchers found that 74% of the patients on MUSE had erections sufficient for intercourse as opposed to 37% of the untreated control group. An advantage of these medications over oral pills (see PDE5 inhibitors) is that they act locally on the penile blood vessels and have no systemic effects (i.e. flushing, headaches, nasal congestion, interaction with other medications, etc.)…that said, injecting medication into your penis could be a bit intimidating.
- Phosphodieseterase type 5 (PDE5) inhibitors are the class of oral medications that have revolutionized the treatment of ED. They include the drugs Viagra (sildenafil), Levitra (vardenafil) and Cialis (tadalafil). These drugs also work by relaxing blood vessels in the penis, thereby increasing blood flow.
- Use of PDE5’s after prostatectomy:
- In a randomized, placebo-controlled, double-blind study researchers reported that 10 mg of daily Levitra (started within 2 weeks after surgery) resulted in improved erectile function over placebo by 9 months after surgery.
- Use of PDE5’s after radiation therapy:
- Positive Study: In a study by Memorial Sloan-Kettering Cancer Center researchers randomized patients prior to radiation therapy to 50 mg of daily Viagra or placebo (starting 3 days before the start of radiation therapy and continuing for 6 months after completing prostate cancer treatment.) They discovered that erectile function was significantly better in the Viagra group up to 24 months after the start of the study. Listen to the study lead author (Dr Zelefsky) discuss these results.
- Negative Study: In a Mayo Clinic and RTOG study, investigators randomly assigned 242 men with prostate cancer to receive tadalafil (5 mg) or placebo daily for 24 weeks starting with radiation therapy (either with external radiotherapy [63 percent] or brachytherapy [37 percent]). Between weeks 28 and 30 after the start of radiation therapy, among evaluable participants, 79 percent who received tadalafil retained erectile function compared with 74 percent who received placebo. A significant difference between groups was also not observed at 1 year (72 percent vs 71 percent). Tadalafil was not associated with improved overall sexual function or satisfaction, and partners of men assigned tadalafil noted no significant effect on sexual satisfaction.
Erectile dysfunction is a common problem affecting a large percentage of men after treatment for prostate cancer. Although we do not have longterm, definitive answers as to whether penile rehab is an effective therapy for ED, it is worth having a discussion about this with your radiation oncologist or urologist prior to prostate cancer treatment. These medications are not inexpensive (retail: $10-20 per day) and they do have side effects, complications and potential contraindications. Your doctor will be able to counsel you on these issues as they pertain to you.