The seminal vesicles (SV) are glands that open into the prostatic urethra and secrete seminal
fluid, which makes up 50 to 80% of semen. They play an essential role in the male
reproductive function. In adults, the size of a seminal vesicle varies from one individual to
another. On average, it is 5 to 6 cm long, 1.5 cm wide and 0.5 cm thick. It has a close
anatomical relationship with Walsh's vascular-nervous pedicle, which extends the
sacro-genital-pubic blades, and is responsible for erection. The reference treatment for
localized prostate cancer can consist of two alternatives: either intensity-modulated pelvic
radiotherapy with treatment of the entire prostate volume and VS, or surgical removal of the
vesiculo-prostatic block in monobloc. It is therefore always extended to the VS.
Magnetic resonance imaging (MRI) is now routinely performed for the initial workup of
prostate cancer, with a diagnostic and prognostic role, as invasion of the VS by cancer is
recognized as a poor prognostic factor. Some radiology centers recommend 3 days of sexual
abstinence to allow a proper seminal vesicle study. Various factors, such as serum
testosterone levels, autosomal dominant polycystic kidney disease, smoking, and certain drugs
such as SILODOSINE, have been identified as factors that can independently vary seminal
vesicle size.
The duration of sexual abstinence since the last ejaculation also appears to be correlated
with seminal vesicle volume. Two recent studies found a correlation between the duration of
sexual abstinence and seminal vesicle volume measured on MRI in a young population (median
age 35.9 and 46.45 years). This population is not superimposable to that of patients managed
for prostate cancer whose average age at diagnosis is 70 years.
However, the control and knowledge of the volume of VS, in this specific population, could
have an interest in the treatment of prostate cancer:
In case of pelvic radiotherapy in order to limit the volume of the organ to be
irradiated, the toxicity induced to the adjacent organs being directly associated to the
delivered dose.
In case of radical vesiculo-prostatectomy, by surgical way, the lateral dissection of
the vasculo-nerveous bands is made more difficult in case of voluminous seminal vesicles
with an increased risk of nerve damage.
Investigators hypothesize that the volume of the VS is correlated with the duration of
abstinence. Thus, evacuation of seminal fluid by ejaculation at a defined time before
curative treatment of prostate cancer, could improve the functional results of pelvic
radiotherapy or surgery.