Erectile dysfunction, one of the consequences of radiation therapy in men undergoing treatment for prostate cancer, may be associated with changes in the volume of the penile bulb (the bottom part of the penis), according to a new study.
The study, “Effect Of Dose And Image Guided Radiation Therapy (IGRT) On Patient-Reported Sexual Function In Prostate Radiation Therapy,” was published in the International Journal of Radiation Oncology.
Prostate radiation therapy can cause erectile dysfunction in patients undergoing this type of treatment, and previous research has suggested that the penile bulb may be related to this negative outcome. However, the relationship between the dose of radiation and changes in penile bulb volume have remained elusive.
To address this matter, researchers compared the changes in penile bulb volume of a subgroup of prostate cancer patients from the CHHiP trial who were treated using prostate image-guided radiation therapy (IGRT) with their self-reported erectile dysfunction after the treatment.
The subgroup included 293 untreated prostate cancer patients who were randomly assigned to receive radiation therapy with or without daily IGRT, with standard or reduced CTV-PTV margins (which define the tumor and target volumes for radiation therapy).
At least two years after the end of radiation therapy, patients were given the EPIC and IIEF-5 questionnaires to evaluate patient sexual function and erectile dysfunction, respectively. Patients also received an additional IIEF-5 questionnaire to retrospectively report on their status before the therapy. Researchers also analyzed parameters of penile bulb volume and developed an algorithm to compare this data with that provided by the questionnaires.
Of the initial group of 293 patients, 182 returned complete questionnaires, but data on their radiation dose was available only for 138. Also, patients who reported severe erectile dysfunction before therapy were excluded, leaving a final group of 90 patients.
The analysis showed that the median time between the end of radiation therapy and completion of the test was of 46.5 months. The team found evidence that patients with higher penile bulb volume and who submitted to higher radiation doses had severe erectile dysfunction or moderate/big sexual problems.
These results not only show that there is indeed a relationship between the penile bulb and erectile dysfunction in patients who undergo radiation therapy, but also that the planning of this type of therapy should perhaps avoid the penile bulb.
According to the authors, this analysis will be carried out in an additional group of patients to confirm the results.
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