Predicting the effect of Viagra after radiation


Phosphodiesterase type 5 (PDE5) inhibitors such as sildenafil (Viagra) are now used regularly as a means to treat patients with erectile dysfunction (ED) following radiation therapy (RT) for localized prostate cancer.

Teloken et al. set out to define predictors of response to sildenafil among such men. Eligible patients had to meet several criteria:

  • Treatment with either three-dimensional conformal external beam radiotherapy (EBRT) or brachytherapy (BT), with or without androgen deprivation (AD)
  • A self-reported ability to have sexual intercourse prior to radiation
  • The onset of ED following radiation
  • No contraindications to use of  sildenafil
  • A willingness to participate in periodic follow-up
  • Completion of  the International Index of Erectile Function (IIEF) evaluation at least 12 months after completion of radiation

Failure to respond to sildenafil was defined as an IIEF erectile function (EF) domain score of < 22.

The results of the study reported by the authors were as follows:

  • 152 patients met all the criteria: 110 in the EBRT group and 42 in the BT group.
  • The average age of the patients was 62 years.
  • The average follow-up was 38 months.
  • The mean radiation dose for EBRT was 78 Gy and for BT was 101 Gy.
  • 35 patients received androgen deprivation.
  • 61 percent of the patients receiving androgen deprivation had exposure only prior to radiation, whereas 39 percent had pre- and post-radiation exposure.
  • The mean duration of androgen deprivation was 4.6 months.
  • The post-radiation IIEF EF domain score at > 24 months was 17.
  • Successful response to sildenafil occurred in 68 percent of men at 12 months after RT, 50 percent at 24 months, and 36 percent at 36 months.
  • On multivariable analysis, predictors of failure to respond to sildenafil were: older age, longer time after radiotherapy, androgen deprivation of > 4 months duration, and a radiotherapy dose > 85 Gy.
  • The type of radiation delivery (i.e., EBRT or BT) was not predictive of sildenafil failure.

The authors conclude that a steady decrease in sildenafil response was seen with increasing duration after radiation therapy, and that several factors were predictive of sildenafil failure.

The “New” Prostate Cancer InfoLink notes that this continuous increase in level of erectile dysfunction  after radiation therapy suggests that the true incidence of ED post-radiation may be surprisingly high when assessed over time. However, it may be extremely difficult to disassociate this effect from the aging of the study population unless studies stratify their patients by age as well as by treatment category: ED is, after all, a normal consequence of aging!

6 Responses

  1. I’ve been through 1 year of ADT (started June 07) and been treated with ultrasound-guided EBRT/IMRT (Sept/Oct 07), after biopsy showed 12/12 cores positive (5 to 70%), no external prostate cancer was detected.

    I’ve not been able to find anyone or any source that will tell me whether or not there will be an orgasm climax during intercourse. I’m assuming that it will be dry, due to the damage during EBRT. To date I have no trouble getting or keeping an erection, but I reach/exceed a pain threshold before climax. There is no feeling of release or pleasure. The erection will slowly go away.

  2. Joe: Have you tried posting this question on the Prostate Problems Mailing List?

  3. Aloha Mike,

    I reviewed the “Site Map” and did not find “Prostate Problems Mailing List”. So, where is this list?

    Thanks,

    Joe

  4. Dear Joe: You can simply click here to join (or to leave) the Prostate Problems Mailing List (which is entirely independent of Prostate Cancer International).

  5. Aloha Mike,
    Perhaps they are having site problems, but I found the PPML site very difficult to navigate, could not find where to post the question, could not find results of a couple of searches, very frustrating, would probably not go back.

    Joe

  6. Aloha Mike,

    Finally figured out how to use the PPML site.

    Thank YOU!

    Joe

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