Many men who have aggressive but localized prostate cancer have to have a radical prostatectomy (RP), where the whole of the prostate gland is removed with the surrounding structures.
The treatment successfully gets rid of cancer in those patients where it is confined to the prostate, with a 10-year survival of 90% or more.
However, there are some side effects, one of the most important being post-operative erectile dysfunction (ED). ED can occur in 14% to 90% of cases, depending on surgical expertise and approach.
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Why Does ED Occur with Radical Prostatectomy?
The prostate is a walnut-sized gland wrapped around the urethra at the very base of the urinary bladder. Damage to the cavernous nerves on either side of the prostate is responsible for post-RP ED.
The risk is reduced but not avoided with nerve-sparing RP. This is due to the local occurrence of inflammation and ischemia following the trauma of cutting the tissue, coagulation of blood vessels, nerve traction, compression of nerves, etc.
All this contributes to cavernous nerve damage that predisposes to hypoxia of the penis, with subsequent apoptosis and fibrosis, resulting in ED.
Robotic-assisted RP allows the surgeon a magnified view of the operating field in three dimensions, along with much more precise movements. As a result, it has been shown, in good hands, to further reduce the risk of ED to about 25% at 12 months. However, this improvement is due in part to the use of phosphodiesterase type 5 inhibitors (PDE5Is) and not just the change in surgical technique.
This fact makes it essential to evaluate and document baseline erectile function for each patient using internationally validated psychometric tools. This will take into consideration the presence of multiple factors that influence erectile function, including cardiovascular risk factors, diabetes, obesity, smoking, chronic kidney disease, and neurological disease.
Men with poor erections at baseline are more likely to have late recovery of erectile function after RP compared to those with normal erectile function.
How Can ED Be Treated After Prostate Surgery?
Despite the development of nerve-sparing techniques, over 50% of men suffer from ED after RP. This has given rise to the concept of penile rehabilitation, which means taking note of the factors that affect erectile function and using a medication, devices, or other means to restore it.
While ED affects 70% to 100% of men after various types of prostate surgery, a significant percentage of men regain their ability to have erections within about 2 years of the nerve-sparing surgery.
If not, there are several options available.
Phosphodiesterase Type 5 Inhibitors (PDE5Is)
Prescription drugs like sildenafil, vardenafil, and tadalafil can all work by improving penile blood flow, thus facilitating an erection. These medications reduce the breakdown of cyclic guanosine monophosphate (cGMP), a cellular signaling molecule, which stimulates the outflow of calcium ions from inside the cell. The result of this movement is the relaxation of the penile smooth muscle and erection.
These drugs are used either nightly or on-demand (to produce an erection just before sexual intercourse). They succeed in a reported 75% of men after nerve-sparing RP but are somewhat less effective after conventional RP. Men with heart problems are not suitable candidates for this treatment.
Alprostadil is a precursor drug that delivers PGE1 which causes the levels of the signaling peptide 3',5'-cyclic adenosine monophosphate (cAMP) within the erectile tissue to increase, causing the same effects as those of the PDE5Is.
It is used either by injection using small needles into the corpora cavernosa of the penis, at the base, or as small suppositories that are inserted into the penile urethra. Some men do not like injecting the penis.
On the other hand, intraurethral insertion can cause local burning and pain, which contribute to the relatively high dropout rate.
Another intracavernosal injection is comprised of papaverine, a PGEi; phentolamine, an alpha-receptor blocker; and PGE1. These three act as vasoactive agents to produce penile engorgement and erection.
Vacuum Erection Devices
Vacuum erection devices (VED) are cylindrical devices that create negative pressure around the penis, as a result of which arterial and venous blood is pulled into the corpus cavernosum, creating an erection which is maintained by putting a band around the base of the penis.
This does not depend on the nervous pathway or nitric oxide secretion. However, the band should be removed within 30 minutes of application as the penile blood becomes hypoxic after this period. Better results over the long term may be obtained with a combination of VED and PDE5Is.
Penile Prosthetic Implants
The penile prosthesis is a small invisible implant first introduced in the 1870s, including a balloon located within the penis and along the penile shaft that can be inflated by a tiny pump in the scrotum.
Reports indicate that in experienced hands it is an effective treatment with excellent satisfaction scores for patients and partners even after 10 years, in the absence of mechanical failure.
Low-Intensity Extracorporeal Shock Wave Therapy
This therapy is based on the principle of inducing local microtrauma so that the body will respond by stimulating the growth of tiny blood vessels into the penis.
This causes upregulation of vascular growth factors and NO synthase, as well as enhancing the function of the smooth muscle cells and endothelial cells.
Cavernous Nerve Interposition Grafting
A Melbourne study showed that microsurgical end-to-side grafting of the sural nerve of the leg to the femoral nerve and the cavernous bodies produced good results. The sural nerve is microsurgically attached to join the femoral nerve to tissue within the corpora cavernosa.
This method of grafting is aimed at restoring the nerve supply to the muscular erectile tissue and enable penile erections. The small study showed that 71% of men had a satisfactory erectile function at 12 months.
The penile erection is surmised to occur because neurotransmitters like acetylcholine and nitric oxide can travel through the new fibers growing along the scaffolding provided by the sural nerve, to the penile tissue.
Other as-yet unproven options that are being tested include stem cells, impulse magnetic field treatment, tissue engineering, and nanoparticles.
It is Not Only About ED
However, it is important to emphasize that erections are not the sole, or even the most important, characteristic of a satisfactory sexual experience.
Orgasms and sexual feelings remain, and a supportive and willing partner can work wonders in regaining sexual satisfaction even in the absence of a full erection.
Psychogenic factors are the single most important factor causing ED, indicating that both partners need to be treated for this simultaneously. This improves the motivation and compliance with the treatment of the patient with ED.
References and Future Reading