Molecular imaging of prostate cancer

Abstract

Prostate cancer is a common malignancy with various treatments from surveillance, surgery, radiation and chemotherapy. The institution of appropriate, effective treatment relies in part on accurate imaging. Molecular imaging techniques offer an opportunity for increased timely detection of prostate cancer, its recurrence, as well as metastatic disease. Advancements within the field of molecular imaging have been complex with some agents targeting receptors and others acting as metabolic intermediaries. In this article, we provide an overview of the most clinically relevant radiotracers to date based on a combination of the five states model and the National Comprehensive Cancer Network Guidelines.

Figure 1.

A 73-year-old-male with T4N1M1a, newly diagnosed prostate adenocarcinoma, Gleason 4 + 4, PSA 8.3. ¹⁸F-FACBC PET/CT scan was ordered for staging purposes because of very high-risk of local disease on clinical assessment and mpMRI (which is not an FDA-approved indication). The scan showed intensely avid local disease in the left prostate (long black arrow) on MIP image (a) and axial PET/CT-fused image (b), mildly avid (uptake above blood pool and below bone marrow reference) in left internal iliac regional pelvic N1 subcentimetre lymph nodes (white arrow head), (c) mildly avid subcentimetre M1a metastatic left lower retroperitoneal lymph nodes (black arrow head), (d) and moderately avid (uptake above blood pool and below liver) mildly enlarged 1.6 cm short axis M1a left periceliac high (above renal veins) retroperitoneal lymph node (long white arrow), (e) Per ¹⁸F-FACBC interpretation criteria, the lymph nodes followed the expected spread pattern for prostate cancer and had uptake above blood pool (nodes <1 cm) or bone marrow (node >1 cm). Mildly avid bilateral inguinal nodes, not typical for spread of prostate cancer, are deemed negative (not shown). There is physiological activity in the head and neck mucosa, liver, pancreas, spleen, bowel and muscle (intense liver and pancreas activity is characteristic for ¹⁸F-FACBC scan). From treatment standpoint, left pelvic and lower retroperitoneal lymph nodes may be treated with extended PLND or extended-field EBRT. However, left periceliac lymph nodes would require systemic treatment with ADT. Thus, the scan provided essential information for patient management. ¹⁸F-FACBCPET, ¹⁸F-fluorocyclobutane-1-carboxylic acid positron emission tomography; ADT, androgen deprivation therapy; EBRT, external beam radiation therapy; FDA, Federal Drug Administration; MIP, maximal intensity projection; mpMRI, multiparametric MRI; PLND, pelvic lymph node dissection.

Figure 2.

A 73-year-old-male with castrate resistant prostate cancer and extensive local, regional nodal and metastatic disease on novel PSMA agent PET/CT [clinical trial NCT02981368 “A PrOspective Phase 2/3 Multi-Center Study of ¹⁸F-DCFPyL PET/CT Imaging in Patients With PRostate Cancer: Examination of Diagnostic AccuracY (OSPREY)”, Progenics Pharmaceuticals, Inc]. The patient was diagnosed with prostate cancer about 20 years ago and treated with brachytherapy. About a decade ago, he experienced biochemical failure and CT showed extensive M1a retroperitoneal nodal disease. The cancer was initially hormone sensitive with PSA becoming undetectable. He eventually developed castrate resistant disease and failed chemotherapy and immunotherapy. MIP PET/CT image (a) shows extensive local, regional nodal and metastatic disease with only one functional right kidney with radiotracer excretion into nephrostomy bag (curved arrow). Axial PET/CT-fused image at the level of kidneys (b) shows functional right kidney, non-functioning severely hydronephrotic left kidney (due to obstruction by nodal disease, not shown), and extensive bilateral M1a retroperitoneal nodal involvement (long white arrow). Axial PET/CT-fused (c) and CT (d) images at the level of prostate show an extensive prostate lesion grossly invading the urinary bladder (long black arrow) and the absence of expected radiotracer in the bladder. Axial PET/CT-fused (e) and CT (f) images at the level of the upper pelvis show regional N1 nodal involvement (white arrow heads). Axial PET/CT-fused (g) and CT images (h) at the level of thoracic spine show a metastatic M1b osseous marrow lesion without CT correlate, which is presumably an early phase prior to adjacent bone response. Axial PET/CT-fused (i) and CT (j) images at the level of sacrum show a metastatic M1b osseous marrow lesion with a faintly sclerotic border indicating response of surrounding bone. Notable sites of physiological activity include the lacrimal glands, salivary glands, liver, spleen and bowel. Normal excretion pattern with intense renal activity and activity in the ureters and bladder is altered in this patient by disease and urinary diversion. MIP, maximal intensity projection; PET, positron emission tomography; PSA, prostate-specific antigen; PSMA, prostate-specific membrane antigen.