Smaller Penis (And Regret) May Follow Prostate Cancer Treatment

Rarely Discussed

Nick Mulcahy

January 07, 2013

Treatments for prostate cancer can result in a little-mentioned adverse effect — a smaller penis, according to a new study.

In addition, men with reduced penile size were significantly more likely to regret treatment than those without size loss.

Reduced penile size is not a common adverse effect of prostate cancer treatment; it occurred in only 25 (2.6%) of the study's 948 men, according to the researchers, led by Paul Nguyen, MD, a radiation oncologist from the Dana-Farber Cancer Institute and Brigham and Women's Hospital in Boston, Massachusetts. Their results were published in the January issue of Urology.

The researchers found significantly more complaints of a shortened penis associated with surgery (P = .004) and radiotherapy plus androgen-deprivation therapy (ADT) (P =.016) than with radiotherapy alone.

The rate of reduced penile size was 3.73% for surgery (19 of 510), 2.67% for radiotherapy plus ADT (6 of 225), and 0% for radiotherapy alone (0 of 213).

This study is "really of interest" because it has a large number of patients and includes more than just surgery, which has been studied most often, writes Luc Cormier, MD, PhD, urologist at the Dijon University Hospital in France, in an accompanying editorial comment.

The study's data on penis size come from a physician-completed questionnaire about their patients who consented to become part of the Comprehensive, Observational, Multicenter, Prostate Adenocarcinoma (COMPARE) registry, which was opened in 2004 at 150 sites in the United States to track biochemical recurrence after primary therapy. About 20% of the men were younger than 60 years, and roughly three quarters were in their 60s and 70s.

The men probably would not mention size loss at clinic visits if "more pressing" issues, such as prognosis and oncologic control, were discussed, say the authors; hence, underreporting was likely.

The adverse effect of penile shortening is "rarely mentioned" by physicians, they point out.

10% or less of doctors who treat prostate cancer routinely discuss reduction in penis size.

"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," Dr. Nguyen told Medscape Medical News. He also said that the potential adverse effect of a smaller penis is well known among clinicians.

If the potential for size loss was more widely discussed, more men might consider active surveillance as a treatment option, Dr. Nguyen acknowledged.

Sexual Functioning Also Involved

A smaller penis has far-ranging effects for a man, according to the study results.

Reduced penile size was significantly associated with more treatment regret (odds ratio [OR], 3.37; P = .0079) and an increased risk for interference with close emotional relationships (OR, 2.36; P = .044) on multivariate analysis, adjusted for age, treatment type, and baseline comorbidity. There was also a nearly significant impact on another measure — the "overall enjoyment" in life.

These data on emotional sequelae were derived from a different questionnaire, which was completed by the patients themselves. In the case of 2 measures ("interference with close relationships" and "overall enjoyment"), the questions were actually rooted in sexual function. Patients were asked, for example, how often their sexual functioning "made it difficult to enjoy your life." Thus, the findings about the emotional sequelae of prostate cancer treatment are related to sexual functioning.

Size Loss: Perceived, Not Measured

This study did not include actual measurements of patients' penises. Instead, the problem of size loss was culled from physician-completed questionnaires about their patients. In effect, a patient had to complain about their "perceived reduction in penile size."

Other studies have put a ruler to work.

In one study, stretched penile length was measured before and after bilateral nerve-sparing surgery; it showed a significant decrease in length at 1 month, from 11.77 to 11.13 cm (J Endourol. 2011;25:65-69).

In a prospective study of men receiving ADT alone as initial therapy for prostate cancer, there was a significant decrease in the mean penile length at 15 months, from 10.76 to 8.05 cm (J Sex Med. 2011;8:3214-3219). That study found no significant relation between potency and penile shortening. However, some researchers have suggested that the loss of erectile function related to ADT might contribute to shortening, note Dr. Nguyen and his coauthors.

The patients' perception of penile length is the key point.

Dr. Cormier does not put much stock in actual measurements, which could be "stressful" for patients. "The patients' perception of penile length is the key point," he writes.

But this is tricky, Dr. Cormier says.

"Sexual activity needs to be thoroughly measured, owing to the obvious relationship with the patients' perception of penile length. Finally, the psychological effect of disease recurrence might modify patients' perception of penile length," he writes.

No validated self-administered questionnaire exploring all these domains exists, Dr. Cormier explains. His speculations do not, however, address a key study finding — that radiotherapy was not associated with any size loss, but surgery and ADT were.

Dr. Nguyen and his coauthors state that radiation could, in fact, cause shrinkage.

They observe that other researchers have speculated that "long-term inflammatory changes to the microvasculature, neural tissues, and structural changes to the corporeal smooth muscle, all resulting from external-beam radiation therapy...can contribute to penile length changes."

It is unclear why penile reduction occurs after surgery. The authors suggest that denervation atrophy associated with erectile dysfunction and possibly fibrosis of the cavernous smooth muscle might occur.

The research was supported by an anonymous family foundation, the Doris Duke Charitable Foundation Clinical Research Fellowship at Harvard Medical School, David and Cynthia Chapin, and a Prostate Cancer Foundation Young Investigator Award. The authors and editorialist have disclosed no relevant financial relationships.

Urology. 2013;81:130-135, 134. Abstract, Editorial comment