Interest of PET-PSMA Imaging Potentialised by Androgen Blockade in Localized Prostatic Adenocarcinoma

The identification of lesions responsible for biological recurrence or persistent biological disease in patients with prostatic adenocarcinoma (PA) remains an outstanding problem due to the lack of sensitivity of standard imaging techniques. The efficacy of empirical radiation therapy of the prostate + pelvis zone in only half of patients with increased PSA suggests an underestimation of lesions.

PET-68Ga-PSMA or PET-PSMA technique showed a clear gain in sensitivity for the detection of lesions in this context compared to PET-Choline which was already more sensitive than standard imaging. It is about 50% for a PSA <0.5 ng / ml vs 20% for a PSA <1 ng / ml for TEP-Choline technique. However, the indication of empirical radiotherapy is raised when the PSA exceeds 0.2 ng / ml. It is therefore still necessary to increase the sensitivity of PET-PSMA.

A flare-up-related effect was observed in a small animal experiment and in a patient after androgen blocking treatment, inducing a sharp increase in the intensity of previously visualized lesions and the appearance of 13 new lesions.

It would therefore be possible to increase the expression of PSMA by the lesions at the origin of the biological recurrence of AP and thus to improve their detection by PET-PSMA after potentiation by short-term androgen blocking by an antagonist of LH-RH.

Inclusion criteria

• Age ≥ 18 years old;
• Hormone-naive patients, initially treated curatively by prostatectomy for prostate adenocarcinoma and having a first or new biological recurrence (PSA greater than 0.2 ng/ml; confirmed on at least two successive dosages in the last 12 months) OR Hormone-naive patients, initially treated curatively by external radiotherapy or by brachytherapy for prostate adenocarcinoma and having a biological recurrence (PSA Nadir + 2ng/ml ; confirmed on at least two successive dosages in the last 12 months ) OR hormone-naive patients treated by surgery or external radiotherapy or brachytherapy for prostate adenocarcinoma but with persistent biological disease (PSA detectable after prostatectomy, or unchanged or increasing PSA after external radiotherapy or brachytherapy);
• Diagnostic recurrence assessment by any information or examination carried out since the ascension of the PSA, not having revealed local recurrence or lymph node lesions which may benefit from to external radiation
• Signed informed consent.

Exclusion criteria

• Patient already treated by hormonotherapy;
• Formal contraindication to hormonotherapy;
• Formal contraindication to external radiotherapy
• Formal contraindication to the Lasilix administration during the PET exams: Hypersensitivity to Furosemide or to one of the excipients, functional acute renal insufficiency, hepatic encephalopathy, urinary tracts obstruction, hypovolemia or dehydration, severe hypokalemia, severe hyponatremia, hepatitis in evolution and severe hepatocellular insufficiency in haemodialysis patient and patient presenting a severe renal insufficiency (creatinine clearance <30 ml / min) due to the risk of accumulation of furosemide, which is then mainly eliminated by the biliary route;
• Significant cardiovascular affection such as myocardial infarction within the last 6 months preceding inclusion, severe rhythm disturbances, stroke within 6 months prior to inclusion, prolonged corrected QT interval with QTc > 450 msecs according to Bazett formula;
• Impossibility to comply with the study follow-up for geographical or psychic reasons.
• Patient under protection of justice (Under tutorship, curatorship or deprived of liberty)