Recent developments in penile cancer imaging

Sentinel Node Methods in Penile Cancer - a Historical Perspective on Development of Modern Concepts

Malignant penile tumors are of squamous cell origin in more than 95% of cases and the occurrence of a distant metastasis without prior inguinal lymph node metastatic deposits is very rare. This makes inguinal lymph node staging very reliable and of great prognostic significance since undiscovered and untreated inguinal metastases may lead to a fatal clinical course. In lack of a sufficiently accurate noninvasive lymph node staging modality, penile cancer relies on surgical lymph node removal for regional staging. In this respect sentinel node biopsy offers a favourable minimally invasive alternative to prophylactic inguinal lymph node dissection which is associated with significant surgery-related morbidity. Today sentinel node biopsy is widely used in surgical oncology within high volume cancers such as breast cancer and melanoma. In rare cancers sentinel node biopsy is also emerging as a minimal invasive staging tool in patients with no obvious lymph node involvement. At several specialized units across Europe sentinel node biopsy has been practiced by dedicated specialist within vulva and penile cancer for more than two decades. In fact, the rare disease penile cancer was a model entity for development of the original sentinel node concept as early as the 1970'es due to work by the Paraguayan penile cancer pioneer, Cabañas, the sentinel node concept was subsequently successfully adapted in breast cancer and melanoma. This turned out mutually beneficial since the sequential development of sentinel node biopsy in penile cancer in the 1990s eventually adopted new insights and added conceptual details from the experiences harvested in the broader clinical application possible in these high-volume diseases. The prerequisite to conceptualising the sentinel node approach was the gradual anatomical and functional understanding of the lymphatic system which in western medicine rooted in ancient Greece and gradually increased in details and comprehension with significant contributions from many great notabilities during the last centuries including Hippocrates, Galen, Fallopio, Malpighi, Virchow, Starling, Cabañas, Hodgkin and Horenblas. Sentinel node biopsy in penile cancer is a complex multimodality procedure involving inguinal ultrasonography by radiologists, precise tracer-injection and interpretation of nuclear images by nuclear medicine physicians, radio-tracer- and dye guided open surgical biopsies by urologists and thorough step-sectioning, immunostaining and accurate lymph node specimen analysis by pathologists. This team effort requires well-tested protocols, experience and good collaboration and in rare diseases this calls for centralization of service.

Physiological models for in vivo imaging and targeting the lymphatic system: Nanoparticles and extracellular vesicles

Imaging of the lymphatic vasculature has gained great attention in various fields, not only because lymphatic vessels act as a key draining system in the body, but also for their implication in autoimmune diseases, organ transplant, inflammation and cancer. Thus, neolymphangiogenesis, or the generation of new lymphatics, is typically an early event in the development of multiple tumor types, particularly in aggressive ones such as malignant melanoma. Still, the understanding of how lymphatic endothelial cells get activated at distal (pre)metastatic niches and their impact on therapy is still unclear. Addressing these questions is of particular interest in the case of immune modulators, because endothelial cells may favor or halt inflammatory processes depending on the cellular context. Therefore, there is great interest in visualizing the lymphatic vasculature in vivo. Here, we review imaging tools and mouse models used to analyze the lymphatic vasculature during tumor progression. We also discuss therapeutic approaches based on nanomedicines to target the lymphatic system and the potential use of extracellular vesicles to track and target sentinel lymph nodes. Finally, we summarize main pre-clinical models developed to visualize the lymphatic vasculature in vivo, discussing their applications with a particular focus in metastatic melanoma.

PET/CT limitations and pitfalls in urogenital cancers

Hybrid FDG PET/CT plays a vital role in oncologic imaging and has been widely adopted for the staging and restaging of a variety of malignancies. Its diagnostic value in urogenital malignancies is less well-known, not at least because of the variable FDG avidity of these tumor entities, the sites of these tumors, and technical challenges associated with sequential imaging of CT and PET. PET/CT interpretation thus can be especially challenging and is associated with many pitfalls, which can lead to both false-positive and false-negative diagnoses as well as incorrect assessment of metabolic change following therapy. Currently, FDG PET/CT is not the standard of care for the initial diagnosis or staging of early-stage or low-risk urogenital cancers; however, it can help evaluate distant metastatic disease, response to therapy, and disease recurrence in high-risk patients. Knowledge of imaging features of tumor metabolic avidity and pitfalls is essential for accurate interpretation.

Contemporary Incidence and Predictors of Occult Inguinal Lymph Node Metastases in Men With Clinically Node-negative (cN0) Penile Cancer

OBJECTIVE

To (1) examine the contemporary incidence of occult inguinal LN metastases and (2) identify predictors of occult inguinal LN metastases to improve selection of cN0 patients for inguinal lymphadenectomy (ILND).

METHODS

We identified 590 men with cTany cN0 cM0 penile cancer who underwent partial/radical penectomy and ILND from 2006-2016 in the NCDB. Rates of pN+ disease were examined, and a multivariable regression model was constructed to identify features associated with pN+ disease.

RESULTS

Tumors were ≤pT1 in 21%, pT2 in 43%, and pT3/pT4 in 24% of patients. A median of 15 (IQR 8-22) LNs were removed at ILND. The overall pN+ rate was 24% and did not vary over the study period. The pN+ rate, stratified by pT stage, varied from 18-33%. On multivariable analysis, only higher tumor grade (OR 2.16; P = 0.02 for grade 2; OR 2.81; P = 0.005 for grade 3-4, versus grade 1) and lymphovascular invasion (OR 3.12; P <0.001) were independently associated with pN+ disease, whereas pT stage was not.

CONCLUSION

The contemporary rate of occult LN metastases in men with cN0 penile cancer remains high at approximately 24%. Our results suggest that high tumor grade and/or lymphovascular invasion are better determinants of lymph node involvement than primary tumor stage.

An overview of the diagnoses and treatments for penile cancer

Penile cancer is a rare malignancy and, as a consequence, it is managed in just a few specialist centres across the UK. This article aims to provide health professionals with an introduction and update on the epidemiology and aetiology of penile cancer, as well as the techniques used to diagnose penile cancer and the current treatment options. The article highlgihts the importance of early diagnosis and the role that the clinical nurse specialist in plays supporting those diagnosed with the penile cancer and their families.