Cialis doesn’t help to maintain erectile function among radiotherapy patients


The degree to which drugs like sildenafil (Viagra) and taldalafil (Cialis) may help patient to maintain erectile function after treatment for localized prostate cancer has long been open to question.

A new paper in the Journal of the American Medical Association now suggests that, at least in men receiving radiation therapy as first-line treatment for localized prostate cancer, patients being treated with a daily dose of taldalafil for 24 weeks (starting at the same time as they started their radiation therapy) did no better than men who were randomized to receive a placebo.

This paper by Pisansky et al. was designed to investigate (a) whether tadalafil preserved erectile function in men treated with radiotherapy for prostate cancer, and (b) whether participant- or partner-reported overall sexual function and sexual and marital satisfaction were affected.

The authors conducted a stratified, placebo-controlled, double-blind, parallel-group study with 1:1 randomization at 76 community-based and tertiary medical centers (all in the USA or Canada). Patients were recruited between November 2009 and February 2012 with follow-up through March 2013.

Patients were asked to complete an International Index of Erectile Function (IIEF) questionnaire prior to initiation of radiotherapy as well as at weeks 2 and 4, between weeks 20 and 24, between weeks 28 and 30, and 1 year thereafter. Patients and their partners could respond also to the Sexual Adjustment Questionnaire and to the Locke Marital Adjustment Test before radiotherapy, between weeks 20 and 24 and weeks 28 and 30, and at 1 year.

The primary outcome of the study was off-drug spontaneous erectile function at 28 to 30 weeks after initiation of radiotherapy. Other (secondary) endpoints included spontaneous erection at 1 year; overall sexual function and satisfaction; partner-reported satisfaction and marital adjustment at 28 to 30 weeks and 1 year; predictors of tadalafil response; and adverse events.

Here are the study findings:

  • 242 patients with intact erectile function were recruited.
  • All patients had been diagnosed with localized prostate cancer.
  • All patients were scheduled for treatment with radiation therapy.
    • 152/242 patients (63 percent) were given external beam radiation therapy
    • 90/242 patients (37 percent) received brachytherapy
  • Patients were randomly assigned to taldalafil or placebo therapy for 24 weeks.
    • 121 patients received tadalafil (5 mg q.d.).
    • 121 patients received a placebo.
  • 221/242 participants provided sufficient data for evaluation.
  • Among the 221 evaluable patients
    • 80 patients assigned to tadalafil (79 percent) retained erectile function at 28 to 30 weeks from initiation of radiation therapy.
    • 61 patients assigned to a placebo (74 percent) retained erectile function at 28 to 30 weeks from initiation of radiation therapy.
    • This 5 percent absolute difference was not statistically significant (P = 0.49).
    • 72 percent of patients assigned to tadalifil retained erectile function at 1 year from initiation of radiation therapy.
    • 71 percent of patients assigned to a placebo retained erectile function at 1 year from initiation of radiation therapy.
    • This 1 percent absolute difference was not statistically significant (P = 0.93)
    • There was no evidence of any significant improvement in overall sexual function or satisfaction among men randomized to treatment with taldalafil.
    • Partners of men randomized to treatment with tadalafil noted no significant effect on sexual satisfaction.
    • Marital adjustment was not significantly improved in participants or partners.

Pisansky et al. conclude that

Among men undergoing radiotherapy for prostate cancer, daily use of tadalafil compared with placebo did not result in improved erectile function. These findings do not support daily use of tadalafil to prevent erectile dysfunction in these patients.

Clearly this study is going to “put a cat among the pidgeons” with respect to the use of PDE-5 inhibitors in the prevention of loss of sexual function among men being treated with radiotherapy for localized prostate cancer. The degree to which it will affect the long-term use of these drugs to stimulate erectile function in men who have been treated for localized prostate cancer is harder to evaluate.

9 Responses

  1. What surprised me was the 71/72% reporting retained erectile function after 1 year. I wonder where they are in 2 years? Is radiation considered less likely to cause ED than surgery?

  2. Dear Clara:

    (1) Yes, in the short term, radiation therapy is less likely to induce ED than surgery in men with good erectile function prior to treatment.

    (2) The question of the actual quality of erectile/sexual function is not well addressed in this study. In other words, how good were the erections most of the time? Some of the tools used to ask about this issue set a pretty low bar for “erectile function”, e.g., “sufficient to accomplish vaginal penetration less than 50% of the time”. We are definitely not talking about the erectile/sexual prowess of 18-year-olds here!

  3. NOT TOO SURPRISED

    As a patient who had to hone my knowledge of radiation before selecting TomoTherapy IMRT last year (and a long-term IADT3 patient), I was aware that some side effects of radiation typically take several years to develop, with erectile dysfunction being one of them. I suspected this study would show that patients in the placebo group would do well unless the study covered a number of years of follow-up, and that’s what the results show, with follow-up limited to just a year. Of course that’s a sharp contrast to prostatectomy outcomes, where function is often severely impacted during much of the first year.

    I’m curious whether anyone has studied use of these drugs when erectile dysfunction does show up in radiation patients, a period probably primarily in the 4 to 7 year range, based on my recollection and contacts. Dr. Mulhall is the Memorial Sloan-Kettering expert in this area for prostate cancer patients, but I don’t recall what he has said for radiation patients. My impression is that he has documented or reviewed studies demonstrating usefulness of these drugs for prostatectomy patients during the first year after treatment. (Neither Dr. Mulhall nor Memorial Sloan-Kettering participated in this study.)

    RISK LEVEL and SCOPE OF EBRT: I’m wondering if the full paper describes the risk level of patients studied. I’m guessing it was a fairly low- and intermediate-risk group, with no or few cases of supplemental pelvic radiation that could have a greater chance of impacting the penile bulb.

    PLUS SUPPORTIVE ADT: Also, high-risk guys, like me, will often be on a long course (18 months for me) of supportive androgen deprivation therapy, which has a strong negative impact on function for the vast majority of us. Intermediate-risk patients are often on a much shorter course of ADT, typically several months. I’m wondering if there were such men in the population studied and whether there was any analysis of that subgroup, a group where this class of drugs might make a difference during the first year.

  4. I’m not sure what to make of this. The Zelefsky et al. study of 50 mg Viagra showed significant improvement in IIEF scores and sexual satisfaction at 12 months, but only sexual satisfaction was significantly better at 24 months. Still, at 24 months, 82% of those taking Viagra vs 56% of placebo patients had functional erections, with or without ED medication.

    I don’t have access to the full text, so it is impossible for me to know if the ages and comorbidities were similar in the two studies. I do wish the researchers on sexual function studies like this would index the scores on the standard tests by age of respondent. In general, men undergoing RT are older, and it would be nice to see measures that correct for normal age-related decline in sexual function.

    Perhaps sildenafil has a greater protective effect than tadalafil? Perhaps the relatively higher dose of sildenafil (50 – 100 mg is the highest dose Viagra) vs tadalafil (5 – 20 mg is the highest dose Cialis) had a greater protective effect? Perhaps 24 or 26 weeks of either ED med is not long enough to confer long-term benefits?

  5. Allen:

    The only thing I can clarify for you is that 5 – 20 mg of tadalafil appears to have the same clinical effect as 50 – 100 mg of sildenafil when used in otherwise healthy men with ED. Thus I doubt if either drug would really have a higher protective effect based on dose and frequency of dosing.

    I do suspect that the fact that many of the men in the Zelefsky et al. were still using sildenafil at 12 and 24 months of follow-up, whereas everyone in this trial stopped taking treatments for ED after 24 – 26 weeks, is a major factor in the difference in resulsts between the two trials.

  6. Just as a point of information, I was using Cialis (20 mg) for a few years prior to my radiation treatment (CyberKnife) 2 years ago. I have not experienced any degradation in erection aided by Cialis since my radiation treatment.

  7. 5 mg Cialis is the higher of the two daily doses (with 2.5 mg) recommended by Lilly. Their “on-demand” doses are 10 mg or 20 mg. 5 mg is only for on-demand dosing for those who have liver problems, etc. 2.5 mg or 5 mg is also the daily dose recommended to treat LUTS associated with BPH.

    For Viagra, Pfizer recommends 50 mg or 100 mg as “on-demand” doses, with 25 mg reserved for older men and those with kidney or liver problems or taking protease inhibitors. Viagra doesn’t really have a “daily dose” similar to Cialis because its half-life is so short that it doesn’t achieve a significant steady-state level in the serum.

    In fact, some men take both the 5 mg daily Cialis and reserve the 50 mg on-demand Viagra as a boost. (see, for example, this paper).

    So in the Zelefsky et al. study, the men were treated with an on-demand dose of Viagra every day, while in the Pisansky study, the men were treated with the lower dose of Cialis. I don’t think we know that these would have equivalent protective effects. I think the conclusion Pisansky draws must be limited to 5 mg tadalafil only and can’t be generalized to higher doses of all PDE5 inhibitors.

  8. I am 55 years old. I was diagnosed with prostate cancer when I was 46! I received hormone therapy and brachytherapy. I take Cialis 5 mg daily for urinary frequency, getting up 5 times a night, etc. … The cialis has helped me a lot and has improved my sex life. Whomever wrote this article is clueless! Probably some insurance company hack?

  9. Dear Jim R.

    The people who wrote this study were well-known and respected members of a major clinical trials group (the Radiation Therapy Oncology Group or RTOG). You may not like the results they report, and you personally may well have done very well with the use of Cialis, but that doesn’t justify your bad manners.

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