Radiotherapy and Erectile Dysfunction Explained

Radiotherapy and Erectile Dysfunction: Causes, Assessment and Treatment

Published: 14 October 2026

Radiotherapy and erectile dysfunction are closely linked, particularly following treatment for prostate, bladder or rectal cancer. Radiation can damage the blood vessels and nerves that control erections, with symptoms sometimes developing gradually over months or years after treatment. Understanding this connection and the available treatment options can help you regain confidence and quality of life.

How radiotherapy and erectile dysfunction are connected

Radiotherapy uses high-energy beams to destroy cancer cells, but it can also affect healthy tissue nearby. When used to treat pelvic cancers—especially prostate cancer—radiation may damage the delicate blood vessels, nerves and tissues that are essential for achieving and maintaining an erection [1][2].

The risk and severity of erectile dysfunction after radiotherapy depend on several factors: the radiation dose, the area treated, your age, and whether you had any erectile problems before treatment. External beam radiotherapy and brachytherapy (internal radiation) both carry a risk, though the onset and progression can differ. Some men notice changes within weeks, while for others erectile function declines gradually over one to three years [2].

It is important to know that radiotherapy-related erectile dysfunction is a recognised side effect, not a reflection of your overall health or masculinity. Many men experience it, and effective treatments are available. Discussing your concerns with your oncologist or GP early on can help you access support and interventions that may preserve or restore erectile function [1].

Why radiotherapy affects erectile function

Erections rely on a healthy blood supply to the penis and intact nerve signals from the brain and spinal cord. Radiotherapy to the pelvis can injure the small arteries that carry blood into the erectile tissue, leading to reduced blood flow. Over time, this vascular damage can cause fibrosis (scarring) and make it harder to achieve a firm erection [2].

Radiation can also harm the cavernous nerves that run alongside the prostate and are crucial for triggering erections. Even when surgeons or radiotherapy teams take great care to spare these nerves, some degree of nerve injury is common. Nerve damage may be temporary or permanent, depending on the dose and technique used [1][2].

Hormonal changes can compound the problem. Some men receive androgen deprivation therapy (hormone treatment) alongside radiotherapy, which lowers testosterone and can reduce libido and erectile function. Psychological factors—anxiety, depression or stress related to a cancer diagnosis—also play a role and can make erectile difficulties worse [1].

Timeline of erectile changes after radiotherapy

Erectile dysfunction may appear soon after radiotherapy or develop slowly over months to years. Early changes might include softer erections or difficulty maintaining them. Late-onset ED, appearing one to two years post-treatment, is often due to progressive vascular damage and fibrosis. Regular follow-up with your healthcare team allows early detection and timely intervention, which can improve outcomes [2].

Assessment and diagnosis of radiotherapy and erectile dysfunction

If you are experiencing erectile difficulties after radiotherapy, your GP or specialist will take a detailed history, asking about the timing of your treatment, other medical conditions (such as diabetes or heart disease), current medications, and lifestyle factors like smoking and alcohol use. This helps identify all contributing causes and tailor treatment appropriately [1][2].

A physical examination may be performed to check for signs of vascular or hormonal problems. Blood tests are often arranged to measure testosterone, blood sugar (to screen for diabetes), cholesterol and sometimes thyroid function. Low testosterone is common after hormone therapy and can be addressed separately if needed [2].

In some cases, your doctor may refer you to a specialist urology or sexual health service for further assessment. Specialist tests—such as penile Doppler ultrasound to assess blood flow—are not always necessary but can be helpful if first-line treatments are ineffective or if the cause is unclear [2].

Lifestyle measures to support erectile function after radiotherapy

Lifestyle changes can improve vascular health and support erectile function, even after radiotherapy. Stopping smoking is one of the most effective steps: smoking damages blood vessels and worsens erectile dysfunction. If you need help quitting, your GP or pharmacist can offer advice and access to stop-smoking services [1][2].

Regular physical activity—at least 150 minutes of moderate exercise per week—improves circulation, boosts mood and helps maintain a healthy weight. Activities like brisk walking, cycling or swimming are all beneficial. A balanced diet rich in fruit, vegetables, whole grains and oily fish supports heart and vascular health, which in turn benefits erectile function [1][2].

Limiting alcohol intake is important, as heavy drinking can worsen erectile problems and interfere with the effectiveness of ED medications. Aim to stay within the UK Chief Medical Officers' guideline of no more than 14 units per week, spread over several days. Managing stress and seeking psychological support—through counselling or support groups—can also make a meaningful difference, particularly if anxiety or low mood are contributing to your difficulties [1][2].

Pelvic floor exercises and penile rehabilitation

Some specialists recommend pelvic floor (Kegel) exercises to strengthen the muscles that support erections. Early use of low-dose PDE5 inhibitors or vacuum devices after radiotherapy—sometimes called penile rehabilitation—may help preserve erectile tissue and blood flow, though evidence is still evolving. Discuss these options with your oncologist or urologist [2].

Treatment options for radiotherapy and erectile dysfunction

Oral PDE5 inhibitor medications are the first-line treatment for erectile dysfunction after radiotherapy. These medicines—sildenafil (Viagra), tadalafil (Cialis), vardenafil (Levitra) and avanafil (Spedra)—work by increasing blood flow to the penis when you are sexually aroused. They do not cause an automatic erection; sexual stimulation is still needed [1][2][3][4][5][6].

Sildenafil is taken about one hour before sex, with effects lasting around four hours. Tadalafil can be used on-demand (at least 30 minutes before, with effects lasting up to 36 hours) or as a lower daily dose. Vardenafil works within 25–60 minutes, and avanafil is the fastest-acting, often effective within 15–30 minutes. Your prescriber will help you choose the most suitable option based on your lifestyle, other medications and any side effects you wish to avoid [3][4][5][6].

If oral tablets are not effective or suitable, second-line treatments include alprostadil (Vitaros cream applied to the tip of the penis, or Caverject injections into the side of the penis) and vacuum erection devices. These options require training and support from a specialist service. In rare cases, a penile implant may be considered. Your GP or urologist can discuss the full range of treatments and refer you appropriately [2][7].

Treatment cautions specific to radiotherapy and erectile dysfunction

PDE5 inhibitors are generally safe and effective after radiotherapy, but certain precautions apply. You must never take these medicines if you are using nitrates (such as GTN spray or isosorbide mononitrate for angina), nicorandil, riociguat, or recreational drugs called poppers, as the combination can cause a dangerous drop in blood pressure [3][4][5][6].

If you take an alpha-blocker for prostate symptoms (such as tamsulosin or doxazosin), there is a risk of dizziness or low blood pressure when combined with a PDE5 inhibitor. You should be stable on the alpha-blocker and start on the lowest dose of ED medication; your prescriber will check this carefully during your consultation [3][4].

Some medicines can interact with PDE5 inhibitors by affecting how they are broken down in the body. Potent CYP3A4 inhibitors—including ritonavir, cobicistat (in some HIV medicines), Paxlovid, ketoconazole, itraconazole and clarithromycin—can raise levels of ED medication and increase the risk of side effects. Dose adjustments or alternative treatments may be needed. Conversely, CYP3A4 inducers like rifampicin, carbamazepine, phenytoin or St John's wort can reduce effectiveness [3][4][5][6].

During your online consultation at Cured Pharmacy, the prescriber will review all your current medications, health conditions and radiotherapy history to ensure any treatment is safe and appropriate for you. Never stop or change a prescribed medicine without consulting your doctor or pharmacist [12].

When to seek further medical advice

If PDE5 inhibitors are not effective after several attempts at the correct dose, or if you experience troublesome side effects, contact your GP or the specialist team who managed your cancer treatment. They can review your medication, check for other contributing factors such as low testosterone, and discuss alternative treatments or referral to a specialist erectile dysfunction clinic [2].

Scientific References

1. NHS. (n.d.). Erectile dysfunction (impotence). NHS website. https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/ [accessed 14 October 2026]
2. National Institute for Health and Care Excellence. (n.d.). Erectile dysfunction. Clinical Knowledge Summaries. https://cks.nice.org.uk/topics/erectile-dysfunction/ [accessed 14 October 2026]
3. Joint Formulary Committee. (n.d.). Sildenafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/sildenafil/ [accessed 14 October 2026]
4. Joint Formulary Committee. (n.d.). Tadalafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/tadalafil/ [accessed 14 October 2026]
5. Joint Formulary Committee. (n.d.). Vardenafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/vardenafil/ [accessed 14 October 2026]
6. Joint Formulary Committee. (n.d.). Avanafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/avanafil/ [accessed 14 October 2026]
7. Joint Formulary Committee. (n.d.). Alprostadil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/alprostadil/ [accessed 14 October 2026]

Information on this page is for educational purposes only and is not medical advice. Prescription treatments require clinical assessment by a UK-registered prescriber. Always consult a qualified healthcare professional before starting or changing any medication.