Lutetium-177-PSMA-617 in Low Volume Metastatic Prostate Cancer

Radioligand therapy (RLT) is a promising new therapeutic approach to treat metastatic prostate cancer. This tumor-specific treatment is directed against prostate-specific membrane antigen (PSMA), which is overexpressed in prostate cancer cells. In the last few years, several lutetium-177 (177Lu, β emitter) labeled PSMA ligands have been developed and are currently applied in nuclear medicine departments world-wide to treat metastatic castrate resistant prostate cancer (mCRPC) patients.

A large retrospective study reported an overall biochemical response rate of 45% following multiple 177Lu-PSMA RLT cycles in mCRPC patients, while 40% of patients already responded after a single cycle. RLT with PSMA ligand PSMA-617 was generally well tolerated and 12% of the patients suffered grade 3 to 4 hematological toxicity. In addition, mild and often transient xerostomia occurred in 8%. These results were confirmed in a smaller scale prospective study published recently.

Although these results are very promising, it is noteworthy that all currently Lu-177-PSMA-617 RLT only has been evaluated in end stage prostate cancer patients to date. In theory, RLT could be more effective in low volume disease because of the very high tumor uptake of radioligands in small lesions. There are no published data so far evaluating the therapeutic effect of Lu-177-PSMA-617 RLT in an earlier stage of the disease. Because of the difference in tumor load between mCRPC patients and patients with low volume metastatic disease, dosimetry and toxicity in these patients need evaluation. Here a clinical trial to investigate the efficacy of Lu-177-PSMA-617 RLT in patients with low volume metastatic prostate cancer, prior to the hormone insensitive state is proposed.

Objective: The aim of this study is to evaluate the dosimetry and toxicity of Lu-177-PSMA-617 RLT, in patients with low volume, hormone sensitive metastatic prostate cancer under treatment condition. Ultimately, the goal of this study is to stabilize previously progressive disease in these patients and to improve the quality of life by postponing the need for androgen deprivation therapy (ADT).

Inclusion criteria

• Histological proven adenocarcinoma of the prostate
• Prior local therapy for prostate cancer
• Biochemical recurrence or clinical progression after local therapy (PSA > 0.2 µg/l),
• PSA-DT < 6 months
• Gallium-68 (68Ga)-PSMA-PET-CT positive metastases in bones and/or lymph nodes (N1/M1ab): ≥1, maximally 10 metastases (at least 1 lesion with a lesion size of ≥1 cm to enable adequate dosimetry studies)
• Local treatment for oligo-metastases with radiotherapy or surgery appears to be no option anymore (due to prior treatment or the location of the metastatic lesions)
• No prior hormonal therapy or chemotherapy; testosteron > 1.7 nmol/l. Exception: local prostate cancer treated with local radiotherapy plus adjuvant ADT; these patients need to be stopped with ADT at least 3 months
• No visceral metastases
• Laboratory values:

• White blood cells > 3.5 x 109/l
• Platelet count > 150 x 109/l
• Hemoglobin > 6 mmol/l
• Alanine transaminase, aspartate aminotransferase < 3 x upper limit of normal
• Modification of Diet in Renal Disease Study glomerular filtration rate ≥ 60 ml/min
• Signed informed consent

Exclusion criteria

• No detectable lesions on the Ga-68 PSMA PET/CT with an uptake level below the liver uptake.
• A known subtype other than prostate adenocarcinoma
• Any medical condition present that in the opinion of the investigator will affect patients' clinical status when participating in this trial.
• Prior hip replacement surgery potentially influencing performance of PSMA PET/CT and nano Magnet Resonance Tomography (nMRI)
• Contra-indication for MRI imaging (claustrophobia, implanted electric and electronic devices (heart pacemakers, insulin pumps, implanted hearing aids, neurostimulators), intracranial metal clips, metallic bodies in the eye)
• Contra-indication for Buscopan (allergy to hyoscine or any other ingredients of this medication, allergy to to other atropines (e.g. atropine, scopolamine), myasthenia gravis, enlarged colon, glaucoma or obstructive prostatic hypertrophy)
• Additional contra-indications for the intravenous injection form of Buscopan (taking blood thinning medication (e.g. warfarin, heparin), narrowing of the gastrointestinal tract, fast heartbeat, angina or heart failure)
• Contra-indication to glucagon (pheochromocytoma)