A recent study published in Urology found men who had been treated for prostate cancer reported having a smaller penis after treatment.

Urology Survey Results

A survey of 948 men who had underwent prostate cancer treatment was performed to investigate negative side effects of the treatment. Their findings were:

• 25 of the men surveyed (2.63 percent) reported experiencing a smaller penis than prior to treatment.

The two highest incidences of treatment related to the reporting of a smaller penis were:

• Prostatectomy (surgical removal of the prostate) – 19 of 510 respondents or 3.73%
• Radiotherapy plus androgen deprivation therapy (ADT) – 6 of 225 respondents or 2.67%
• There was NO report (0.00%) of loss in penis size from the 213 survey respondents who were treated with radiotherapy only.

Findings from Other Studies

Although 2.63% of men in the Urology survey may not seem like a significant amount, there have been other studies conducted, which have found similar findings, confirming this potential side effect.  In a study conducted by the Journal of Endourology, researchers found:

• For men who reported a penis length loss, this loss ranged between 2.5 and 3.5 centimeters (+/- an inch) after treatment for prostate cancer.

While the Urology study respondents reported an average of a third of an inch, this is still a side effect men should be aware of the potential, associated with the different prostate cancer treatments.

A study published in the Journal of Sexual Medicine, in 2011, found there was a significant decrease in average penis length, for patients receiving ADT alone.

• At 15 months, mean penis length had decreased from 10.76 cm to 8.05 cm

The Unknown Side Effect

Paul Nguyen, M.D., lead study author of the Urology study and radiation oncologist at the Dana-Farber Cancer Institute and Brigham and Women’s Cancer Center in Boston, notes that the real issue lies in the lack of patient knowledge regarding this potential side effect.

As Dr. Nguyen states, “I think what our study brings home is that this is a real problem and it does affect men. Many of the guys who underwent treatment for their cancer had never even heard about this effect—so this is something that we, as doctors, should be talking about with our patients.”

The Cause of the Penis Shrinkage?

the cause behind this reported shrinkage after prostate cancer treatment is still only theoretical. Dr. Nguyen surmises, “In terms of surgery, we can only assume that since you’re cutting out the prostate and putting things back together again, there’s a little bit of tugging there. And with the hormones, there’s probably some type of shrinkage, or some type of fibrosis occurring that could result in a change in size.”

In a MedScape Medical News interview, Dr. Nguyen stated, “I would think that 10% or less of doctors who treat prostate cancer routinely discuss reduction in penis size as a possible side effect of therapy.” This is despite the fact, Dr. Nguyen noted, that penis shrinkage is a well-known, potential negative side effect.

In the end, knowing this potential side effect should help patients make a more informed decision about their course of treatment. Prostate cancer patients should discuss these findings with their doctors and use the knowledge when determining which form of treatment is best for them.