Genitourinary: advanced

Focal therapy (FT) has emerged as an alternative to whole-gland radical treatments with the objective to reduce treatment-related toxicity by sparing prostatic tissue. The FT approach stands on the concept of identifying and treating de index lesion. Selection criteria, optimal treatment modalities and follow-up strategies remain divergent across published series. A recent consensus from field-experts brings guidance to focal treatment strategies in PCa while standardizing the selection criteria and follow-up schemes. Efforts are being made to improve di agnostic tools to optimize patient selection. Multiparametric MRI represents the cornerstone imaging tool for guided diagnostic, treatment and follow-up of these patients. With further development of image-guided diagnostics and deployment of transperineal prostate mapping (TTMB) and MRI-ultrasound fusion biopsies, the histological accuracy at diagnosis has increased with optimal risk definitions and patient selection. Post-ablation surveillance protocols entail monitoring residual post-ablated and preserved tissue. It should be noted that while serum prostate-specific antigen (PSA) kinetics is considered a reliable tool for following patients after local whole-gland treatment, its role after focal therapy is yet to be defined and the thresholds for defining success and failure have not been defined. Key energy sources delivering FT for PCa include cryotherapy, high-intensity focused ultrasound (HIFU), irreversible electroporation (IRE), photodynamic therapy (PDT) and focused laser ablation. In the future, the natural history of non-index lesions in the post ablative setting needs to be addressed. Combined immunological or hormonal interventions could be considered to further improved cancer control of FT.

Successful focal treatment of prostate cancer requires accurate anatomical localisation which can only be provided by Mp MR. Exclusion of disease in the rest of the prostate is also essential. Mp MRI technique is well established and documented in Pirads vs2. However despite this scan quality remains variable. The assessment of quality will be discussed along with the current status of tumour detection within the gland. The size, position and concordance of the MR target with histological target will be discussed. Critical to the success of focal ablation is the communication of a well defined target. The various techniques available to deliver this are discussed along with contouring techniques.

In recent years, focal therapy of prostate cancer has gained great interest from both health care professionals and patients. Irreversible electroporation (IRE) has emerged as a promising technique for tumor ablation and is currently one of the most intensively studied technologies. IRE refers to the generation of permanent, nanoscale pores in the cell membrane by ultra-short, high voltage impulses, resulting in cell death. Features that make this technique particularly attractive comprise its negligible thermal effect on tissue and the lack of connective tissue destruction distinctive of thermal ablative techniques. Available data from clinical studies indicate IRE as a safe and feasible technique for treatment of selected patients suffering from localized prostate cancer, with limited genitourinary toxicity and promising short-term oncological results. Herein we will to review the rationale, as well as the preclinical and clinical data supporting the use of IRE for the treatment of prostate cancer. Furthermore, we will discuss the importance of patient’s selection and pretreatment workup with emphasis on the value of magnetic resonance imaging (MRI) for treatment planning.

Renal physiology is complex with two compartments functioning under highly different conditions. The cortex is highly perfused with a high level of oxygen, whereas the medulla shows a poor perfusion level and works under hypoxic conditions. Water movements are multiple along the nephrons to maintain normal homeostasis. Glomerular filtration rate is a major marker of renal function, but its measurement is complex to be obtained in clinics. All these parameters can be approached using functional MRI with DCE, DWI, and BOLD. However, validation of these tools and their impact on patient management still requires further prospective studies. Some of these techniques may reflect changes within the extracellular matrix of renal tissue during the process of renal scarring.

Multiparametric magnetic resonance imaging (mpMRI) of the prostate combines T2-weighted MRI (T2w) with functional techniques such as diffusion-weighted MRI (DWI) as a marker of cellular density, and dynamic contrast-enhanced MRI (DCE) to assess neoangiogenesis. The minimal technical requirements for these techniques have been described in the Prostate Imaging, Reporting and Data System (PI-RADS) by the American College of Radiology and the European Society of Urogenital Radiology. T2w MRI detects prostate cancer as low signal-intensity (SI) areas in the peripheral zone (PZ) or transition zone (TZ). It provides sensitivity up to 85% for overall prostate cancer detection, but lacks specificity. DWI primarily detects higher-grade prostate cancers as areas of restricted diffusion (high SI on high b-value images; low SI on ADC maps) and improves the overall specificity. DCE detects cancers because of their early and rapid enhancement after contrast administration, but is useful for the PZ only, due to false-positive enhancement of benign prostatic hyperplasia in the TZ. Reporting of mpMRI has been standardized using the PI-RADS 5-point assessment scale, estimating the likelihood of clinically significant prostate cancer. Prostate biopsies directed to mpMRI-detected lesions have shown to be able to decrease the overall number of prostate biopsies, to increase detection of clinically significant prostate cancer and to decrease overdiagnosis of clinically insignificant prostate cancer. mpMRI-guided biopsies are currently recommended in the setting of rebiopsy after a previously negative biopsy, but evidence has been accumulating showing that mpMRI-guided biopsies are equally useful in biopsy-naïve men.

The standard MRI uterus protocol includes axial SE T1WI with a large FOV to evaluate the entire pelvis and upper abdomen for lymphadenopathy as well as bone marrow changes and high-resolution FSE T2WI in the sagittal, axial and coronal planes. Other extra planes and imaging sequences are specific and designed to answer a specific clinical question. Functional MRI sequences such as DCE-MRI and DW-MRI are now part of routine protocols. DCE-MRI is very useful for assessment of the depth of myometrial invasion in endometrial cancer. DW-MRI is now part of routine MRI protocol for evaluation of uterine malignancies. It should be performed at two or more b-values, which include one or more low b-values (50-100 s/mm²), since perfusion contribution to diffusion is then eliminated, and a very high b-value (750-1000 s/mm²). Both breath-hold and non-breath-hold DW sequences can be used. However, the type of DW sequence differs among manufacturers and the radiologist should be familiar with the strengths and limitations of their own scanners. A combination of DWI with conventional MRI sequences improves lesion detection and the radiologist confidence in imaging interpretation. DW-MRI can be useful for accurately determining the depth of myometrial invasion in endometrial cancer. In addition, ADC values are inversely related to the cellularity of tumours which may be useful for distinguishing between benign and malignant tissues and for monitoring tumour response to treatment in cervical cancer.

CT is currently the imaging modality of choice for the evaluation of renal masses. The advantages of CT are its widespread availability, high speed of acquisition, high spatial resolution and isotropic imaging. MRI can be a powerful problem-solving tool in clinical practice for characterisation of renal masses, especially for characterisation of lesions with indeterminate enhancement at CT and of lesions in which a small amount of fat is suspected. Like CT, MRI provides excellent anatomic information on the evaluation of renal lesions. Moreover, unlike CT, advanced MRI techniques can provide information about tissue structure and function without exposure to ionising radiation and without using iodinated contrast. The disadvantage of MRI compared to CT is the longer examination time. Optimal MDCT protocol for renal masses includes a noncontrast phase followed by postcontrast acquisitions with corticomedullary, nephrographic and delayed phases of enhancement at approximately 40 seconds, 90 seconds and 7 minutes after contrast injection. The nephrographic phase is acquired for assessing the presence of a renal lesion and its enhancement, and is therefore sufficient for detection and characterisation of renal lesions. Corticomedullary and urographic phases are often performed to provide additional information for presurgical planning. Optimal MRI protocol for renal mass evaluation includes TSE T2-weighted imaging, TSE T1-weighted imaging with and without fat suppression, T1-weighted opposed-phase imaging (with in-phase and out-of-phase sequences) for the detection of microscopic fat, DWI, fat-suppressed 3D T1-weighted gradient-echo acquisition before and after administration of intravenous gadolinium contrast in corticomedullary, nephrographic and urographic phases, and subtraction imaging.

Imaging is the main source of detection of renal masses. Differenciation between complex cystic and solid masses is not always straightforward and may require several contrast-enhanced methods, and DCE-MRI and CEUS are more sensitive for that purpose. Considering cystic masses, Bosniak classification is required. Considering solid masses, characterization of fat-rich angiomyolipomas is based on plain CT, but fat-poor AMLs can be distinguished from carcinomas by multiparametric MRI only. Multiparametric MRI includes chemical shift gradient echo (GRE) sequences, signal intensity on T2-weighted images, DCE sequences, diffusion-weighted sequences and late contrast-enhanced images. Using different combinations of two or several parameters, now makes it possible to clearly distinguish some renal tumours such as fat-poor AMLs, papillary carcinomas and clear cell carcinomas, the latter being difficult to separate from oncocytoma when a central scar is absent. A larger validation of all these combinations is still necessary to define those having a clinical significance for routine practice. Percutaneous biopsy remains mandatory before such a validation, as soon as pathological result is supposed to have an impact on tumour management.

Accurate CT- or MRI-based staging of the two most common malignant neoplasms involving the kidneys, renal cell carcinoma (RCC) and transitional cell carcinoma (TCC) is an important prerequisite for surgical decision-making, especially in the early stages of the disease. The TNM staging system is particularly different between RCC and TCC regarding the T-stage. Tumour size and invasion of the perirenal fat are important criteria for local staging of RCC, whereas invasion of the muscular layer of the renal collecting system and invasion into the renal parenchyma are important criteria for staging TCC, the latter being more complex based on imaging as compared to RCC. Different organ-preserving strategies are evolving, especially for treatment of RCC (e.g. local excision versus partial nephrectomy). Also, important additional information such as detailed vascular anatomy is needed by the surgeon, which has impact on the respective preoperative imaging protocol.