Sperling Prostate Center

Another Reason to Reconsider Radiation Treatment: Low Testosterone

UPDATE: 11/19/2021
Originally published 8/15/2017

Does radiation therapy for prostate cancer lower a patient’s testosterone level? Our 2017 blog (below) cites a then-new study published by a multi-center research team, showing that 75% of men whose prostate cancer (PCa) was treated with beam radiation alone had a drop in testosterone. The effect was measurable as early as 6 months; during the average follow-up of 6 years, nearly 63% recovered to at least 90% of pre-treatment levels. What’s noteworthy is that none of the patients received androgen deprivation therapy (ADT or chemical castration), which might have accounted for this effect.

Our original blog is supported by a 2020 paper published by Mortazaee, et al.[i] on the effect of PCa radiation therapy on testosterone levels. They reviewed and analyzed data from 12 studies that were relevant to this topic. Despite variations in the radiation dose administered, “Combining the findings from 12 studies, it was found that prostate cancer radiotherapy leads to a significant reduction in the testosterone level.” However, this effect was greater with conventional beam radiation, IMRT (Intensity-Modulated Radiation Therapy), and SBRT (Stereotactic Body Radiotherapy) than with proton beam radiation. Keep in mind that both IMRT and SBRT are supposed to be more precise than conventional external beam radiation, but apparently these modalities can impact testosterone. This likely results from the scatter effect of radiation on the testicles, which manufacture male hormones.

As for proton beam, Hattori et al. (2021)[ii] report that image-guided proton therapy (IGPT)—with or without ADT—did not seem to reduce testosterone levels in low-risk patients, though erection hardness was somewhat diminished. However, for higher-risk patients who also received ADT, their levels dropped but gradually began to recover after ADT was discontinued.

It’s also worth noting that not just the testicles, but penile structures can also receive damaging radiation that may account for developing ED many months or years following exposure to radioactivity:
“Corpora cavernosa, neurovascular bundle, and penile vasculature injuries are all involved in erectile dysfunction (ED) after radiation exposure.”[iii]


Men with localized prostate cancer (PCa) are usually given three treatment choices: radical prostatectomy (RP), external beam radiation therapy (EBRT) or Active Surveillance (AS). Although patients are rarely told about minimal-to-noninvasive treatments that can be applied as focal therapy, it’s somewhat heartening that urologists and radiologists are increasingly supportive of AS for low-risk patients. This is good, because it avoids overtreating insignificant PCa and preserves urinary and sexual function until clinical factors would indicate a need for treatment.

These days, it seems like all PCa patients are aware of the possible side effects of RP and EBRT. The difference between those two modalities is a kind of “pay now or pay later” choice. RP (“pay now”) more frequently results in upfront post-treatment urinary incontinence and ED, with the hope that things will improve in a year or less. EBRT (“pay later”) has almost no upfront side effects other than fatigue and possibly some minor bowel irritation, but years down the line there could be urinary tract irritation, ED, and risk of secondary bladder or bowel cancers. However, a lot of patients are willing to have radiation or seed implants, because they don’t want the chance of surgical side effects. They prefer to take their chances further down the line.

A new international, multi-center journal article by Pompe et al. (2017)[iv] reveals that EBRT has a sneaky side that has only rarely been studied: it leads to a drop in normal testosterone levels. Testosterone is measured by means of a blood test, so the results are usually referred to as serum testosterone levels. For this study, 248 patients who underwent EBRT from 2002 to 2014 had their pre-treatment (baseline) serum testosterone levels recorded, then they were reassessed after treatment according to each center’s protocol. The average follow-up was 72 months (6 years).

Here are the findings:

  • 186 patients (75%) showed a drop in testosterone after radiation.
  • Average time to the first measured drop was 6.4 months.
  • 112 (45.2%) developed insufficient testosterone, a condition called hypogonadism.
  • Of all who had a drop in testosterone, 117 (62.9%) recovered “to at last 90% of baseline levels”.

Thus, while most patients whose testosterone is affected will eventually recover, the article’s summary is somewhat shocking: “Our findings indicate that up to 75% of patients treated with EBRT monotherapy [meaning radiation alone, no hormones or other additional treatment] will have a profound testosterone decrease, with up to a 40% increase in rates of biochemical hypogonadism [insufficient serum testosterone]…” Perhaps what’s most sobering is the realization that since the testes produce testosterone, the scatter effect of radiation affects how well the testes are able to function until they recover from radiation exposure.

The Canadian Cancer Society notes: “The testicles are very sensitive to the effects of radiation. Radiation can reduce the number of sperm produced or damage sperm and affect their ability to function. Temporary or permanent infertility (inability to father a child) can occur because of radiation to the testicles.”[v] Even though EBRT for prostate cancer is not directly aimed at the testicles, the Pompe study demonstrates that not just sperm production can be affected by radiation, but the very hormone that defines masculinity has a high risk of a steep decrease.

Patients who have EBRT should be made aware of the risks they face, including late onset urinary, sexual or bowel complications in addition to effects on sperm production. Yet those who choose AS take a different kind of chance, since they are hoping to hold off on treatment as long as possible but not to the point where they miss a treatment window.

It’s no wonder that more PCa patients are turning to focal treatments that will control their disease but avoid diminishing their manhood and lifestyle.

NOTE: This content is solely for purposes of information and does not substitute for diagnostic or medical advice. Talk to your doctor if you are experiencing pelvic pain, or have any other health concerns or questions of a personal medical nature.

[i] Mortezaee K, Motallebzadeh E, Milajerdi A, Farhood B et al. The Effect of Prostate Cancer Radiotherapy on Testosterone Level: A Systematic Review and Meta-analysis. Anticancer Agents Med Chem. 2020;20(6):636-642.
[ii] Hattori Y, Iwata H, Nakajima K, Nomura K et al. Changes in sexual function and serum testosterone levels in patients with prostate cancer after image-guided proton therapy. Radiat Res. 2021 May 12;62(3):517-524.
[iii] Stember DS, Mulhall JP. The concept of erectile function preservation (penile rehabilitation) in the patient after brachytherapy for prostate cancer. Brachytherapy 2012;11:87-96.
[iv] Pompe RS, Karakiewicz PI, Zaffuto E, Smith A et al. External beam radiotherapy affects serum testosterone in patients with localized prostate cancer. J Sex Med. 2017 May 22. pii: S1743-6095(17)31140-2. doi: 10.1016/j.jsxm.2017.04.675. [Epub ahead of print]
[v] http://www.cancer.ca/en/cancer-information/diagnosis-and-treatment/radiation-therapy/side-effects-of-radiation-therapy/radiation-to-the-pelvis/radiation-effects-on-men/?region=sk#ixzz4ihCbWKDL


About Dr. Dan Sperling

Dan Sperling, MD, DABR, is a board certified radiologist who is globally recognized as a leader in multiparametric MRI for the detection and diagnosis of a range of disease conditions. As Medical Director of the Sperling Prostate Center, Sperling Medical Group and Sperling Neurosurgery Associates, he and his team are on the leading edge of significant change in medical practice. He is the co-author of the new patient book Redefining Prostate Cancer, and is a contributing author on over 25 published studies. For more information, contact the Sperling Prostate Center.

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