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.

Inclusion Criteria:

• Patient whose age ≥ 45 years
• French speaking patient
• Patient performing a prostate MRI for suspected prostate cancer

Exclusion Criteria:

• History of curative treatment for prostate cancer (radical prostatectomy, external radiotherapy, brachytherapy, HIFU, cryotherapy)
• Patient under guardianship or curatorship
• Patient deprived of liberty
• Patient under court protection
• Patient objecting to the use of his or her data for this research

Patient performing a prostate MRI for suspected prostate cancer, between 07/06/2021 and 30/10/2022.