Indium-111 capromab pendetide (ProstaScint) uptake in neurofibromatosis

Increased Prostate-Specific Membrane Antigen Uptake in Neurofibromatosis

A 51-year-old man with 30-year neurofibromatosis and 2-month elevated prostate-specific antigen and back pain underwent a Ga-prostate-specific membrane antigen (PSMA) PET/CT scan for possible prostate cancer. Prostate-specific membrane antigen PET/CT imaging showed no abnormal uptake of the prostate. However, in addition to PSMA uptake in his left lung, thorax, and right ilium, which was confirmed being a lung squamous cell carcinoma by a lung biopsy, widespread uptake was also observed in his skin fibroma lesions. This case demonstrates that benign neurofibromatosis could have uptake of PSMA.

Targeting prostate cancer: Prostate-specific membrane antigen based diagnosis and therapy

The high incidence rates of prostate cancer (PCa) raise demand for improved therapeutic strategies. Prostate tumors specifically express the prostate-specific membrane antigen (PSMA), a membrane-bound protease. As PSMA is highly overexpressed on malignant prostate tumor cells and as its expression rate correlates with the aggressiveness of the disease, this tumor-associated biomarker provides the possibility to develop new strategies for diagnostics and therapy of PCa. Major advances have been made in PSMA targeting, ranging from immunotherapeutic approaches to therapeutic small molecules. This review elaborates the diversity of PSMA targeting agents while focusing on the radioactively labeled tracers for diagnosis and endoradiotherapy. A variety of radionuclides have been shown to either enable precise diagnosis or efficiently treat the tumor with minimal effects to nontargeted organs. Most small molecules with affinity for PSMA are based on either a phosphonate or a urea-based binding motif. Based on these pharmacophores, major effort has been made to identify modifications to achieve ideal pharmacokinetics while retaining the specific targeting of the PSMA binding pocket. Several tracers have now shown excellent clinical usability in particular for molecular imaging and therapy as proven by the efficiency of theranostic approaches in current studies. The archetypal expression profile of PSMA may be exploited for the treatment with alpha emitters to break radioresistance and thus to bring the power of systemic therapy to higher levels.

Radiolabeled enzyme inhibitors and binding agents targeting PSMA: Effective theranostic tools for imaging and therapy of prostate cancer

Because of the broad incidence, morbidity and mortality associated with prostate-derived cancer, the development of more effective new technologies continues to be an important goal for the accurate detection and treatment of localized prostate cancer, lymphatic involvement and metastases. Prostate-specific membrane antigen (PSMA; Glycoprotein II) is expressed in high levels on prostate-derived cells and is an important target for visualization and treatment of prostate cancer. Radiolabeled peptide targeting technologies have rapidly evolved over the last decade and have focused on the successful development of radiolabeled small molecules that act as inhibitors to the binding of the N-acetyl-l-aspartyl-l-glutamate (NAAG) substrate to the PSMA molecule. A number of radiolabeled PSMA inhibitors have been described in the literature and labeled with SPECT, PET and therapeutic radionuclides. Clinical studies with these agents have demonstrated the improved potential of PSMA-targeted PET imaging agents to detect metastatic prostate cancer in comparison with conventional imaging technologies. Although many of these agents have been evaluated in humans, by far the most extensive clinical literature has described use of the ⁶⁸Ga and ¹⁷⁷Lu agents. This review describes the design and development of these agents, with a focus on the broad clinical introduction of PSMA targeting motifs labeled with ⁶⁸Ga for PET-CT imaging and ¹⁷⁷Lu for therapy. In particular, because of availability from the long-lived ⁶⁸Ge (T_1/2=270days)/⁶⁸Ga (T_1/2=68min) generator system and increasing availability of PET-CT, the ⁶⁸Ga-labeled PSMA targeted agent is receiving widespread interest and is one of the fastest growing radiopharmaceuticals for PET-CT imaging.

Detection of a non-Hodgkin's lymphoma by capromab pendetide scintigraphy (ProstaScint) in a patient with prostate carcinoma

A 77-year-old man with Gleason score 7 prostate cancer, after radical prostatectomy, in whom the prostate-specific antigen level increased to 5.0 ng/mL 8 years later, underwent a ProstaScint scan. Radiotracer deposition was noted in the prostatic "fossa," highly suspicious of recurrence. An additional focus in the mid abdomen was suspicious of adenopathy. Computed tomography disclosed an abdominal mass that, at biopsy, proved to be a malignant B-cell lymphoma. That lesion resolved after chemotherapy, and the prostate-specific antigen level substantially decreased with hormonal treatment. The possible association of prostate cancer and lymphoma is discussed.