Characterising Metastatic Penile Cancer Using Molecular Imaging - Hybrid MRI-PET [MRI-PET]

Penile cancer is a neglected area in terms of clinical and molecular research due to the relatively low incidence of the disease (age standardized incidence is 0.3 - 1 per 100,000 men in European countries and the USA). Inguinal nodes are impalpable in up to 80% of penile cancer patients on presentation. However, 20% of these will harbour occult metastases. Therefore radical inguinal lymphadenectomy, with its significant associated morbidity of up to 70% (and mortality), is an unnecessary surgical procedure in the majority of patients. There are presently only limited data available from small series pertaining to the role of radiological imaging modalities establishing the presence of lymph node metastases, particularly micrometastases, in patients with squamous cell carcinoma of the penis. Thus there is no clear role at the moment for radiological investigations in staging men with impalpable inguinal lymph nodes at presentation. Dynamic sentinel lymph node biopsy is an invasive procedure which utilizes lymphoscintigraphy but still requires surgical excision of the lymph nodes.

Simultaneous PET and MRI using new hybrid MRI-PET systems promises optimal spatial and temporal co-registration of structural, functional, and molecular image data. The theoretical advantages of hybrid MRI-PET scanning compared to CT-PET are better soft tissue resolution, which is advantageous for the small lymph nodes, and also decreased radiation exposure. Also, local staging of the primary penile tumour could be performed simultaneously with the inguinal lymph nodes using MRI-PET. If effective, MRI-PET would provide a single non-invasive imaging test that would replace dynamic sentinel lymph node biopsy (which is operator dependent, involves a general anaesthetic, in-patient hospital stay and has associated morbidity) in the detection of micrometastatic deposits in those patients with cN0 (impalpable inguinal lymph nodes) disease. In addition to this, a single MRI-PET sequence will also stage the primary lesion.

University College London Hospital (UCLH) manages the largest number of penile cancer patients in the United Kingdom (UK). Hybrid MRI-PET is a new imaging modality which could result in significant cost savings, and more importantly, avoid invasive operative procedures necessitating in-patient hospital stay (with the associated potential for significant morbidity). UCLH currently has the only hybrid MRI-PET scanner in the UK. This research is unique and groundbreaking and could have a dramatic impact for penile cancer patients. Additionally, as serum, blood and frozen tissue from this cohort of patients will be collected and stored , this will provide an extremely valuable resource for future translational studies.