Emerging technologies in uroradiologic imaging

Patterns of recurrence and surveillance strategies for renal cell carcinoma following surgical resection

Renal cell carcinoma (RCC) remains one of the most lethal urologic malignancies, with up to 40% of patients eventually dying of cancer progression. Despite advances in the diagnosis, staging and treatment of patients with RCC, approximately a third of patients who undergo surgery for clinically localized RCC will suffer a recurrence. Timely identification of recurrences following surgical extirpation is imperative in the treatment of these patients. RCC is known to metastasize through hematogenous routes of spread to distant organ sites and via lymphatic channels to regional lymph nodes. The path of tumor escape is associated with diverse clinical outcomes and a unique tumor biology. A consensus on surveillance regimens for patients following surgical resection of localized disease is lacking. The most extensively used system for providing prognostic information regarding survival and recurrence of disease has historically been the tumor-node-metastasis (TNM) classification system. As a result, most contemporary surveillance protocols have tailored follow-up regimens according to stage-based stratifications. Numerous studies have recently demonstrated that certain clinical and histopathological factors can improve the prediction of tumor recurrence. The incorporation of these prognostic factors into stage-based stratification models should be better than stage alone in attempting to provide a rational approach to identifying treatable recurrences while minimizing unnecessary exams and tests, as well as patient anxiety. Advances in the understanding of the pathogenesis, behavior and molecular biology of RCC have paved the way for developments that may enhance early diagnosis and prognostication, and improve survival for patients. Lastly, molecular markers should, in the future, revolutionize surveillance protocols for RCC by tailoring follow-up to specific molecular classifications.

Lymph node staging in prostatic carcinoma revisited

Despite presumed curative operation almost one-third of patients with prostatic carcinoma relapse. One obvious reason is that the preoperative lymph node staging is not sufficiently effective. Imaging modalities (CT and NMR) have not resolved the problem. Presently lymphadenectomy is not recommended in patients with Gleason score <7 and PSA <20 ng/ml owing to the low frequency of positive nodes. However, these data are based on experience with limited dissection. Results from extended dissection reveal a higher rate of metastases than previously found. The results from extended dissections showed that more than half of the diagnosed lymph node metastases were found outside the generally recommended regions. The drawback is the higher complication rate that follows. Thus the staging can be improved but if this translates into a survival benefit it needs to be addressed in controlled trials. Alternative techniques for lymph node staging have recently been developed. The sentinel lymph node (SLN) method has been tested and proved feasible. The results corroborated those of extended dissection, namely that the obturator region is insufficient to reflect the field of metastases. High-resolution MRI with magnetic nanoparticles can detect small and otherwise undetectable lymph-node metastases. Positron emission tomography (PET), using acetate or choline as tracers, has performed better than fluoro-2-deoyglucose for detection of relapsing prostate cancer after radical prostatectomy. Studies have also started to assess its role for lymph node staging. In summary, lymph node staging has to cover a larger anatomical field than routinely used. Whether surgical dissection can be replaced by the new imaging modalities is presently under investigation.

Imaging in genitourinary cancer from the urologists' perspective

It is well established that advances in imaging may lead to early cancer detection, more accurate tumour staging and consequently adequate treatment, better monitoring of the disease and enhanced surveillance for recurrences after treatment. This manuscript reviews the current use of imaging in genitourinary cancer and explores the impact of imaging findings in clinical management. Additionally, an effort has been made to present the emerging imaging modalities and also their possible role in diagnosis and treatment of these cancers.

Nuclear Medicine Studies of the Prostate, Testes, and Bladder

During the last decade, there has been a significant advancement in imaging of urologic diseases. Transrectal ultrasound (TRUS), computerized tomography (CT), magnetic resonance imaging (MRI), magnetic resonance spectroscopy (MRS), and positron emission tomography (PET) are still experiencing new developments in urology. Despite these many technological advances, the initial diagnostic procedure for a patient with suspected prostate cancer (PC) is multiple site blind prostate biopsies. There is a need for a noninvasive metabolic imaging modality to direct the site of biopsy to decrease the sampling error. MRS seems promising but as it is a costly and more time-consuming test, further studies are needed to evaluate its clinical utility. Currently, PET does not play any role to direct biopsy. Acetate and choline appear to be better tracers than FDG for the detection of a prostate lesion, however, further well-organized studies are needed before any of these agents can be used clinically. Incidental detection of intense focal uptake in the prostate during whole body PET scanning should be evaluated with prostate-specific antigen (PSA) and TRUS-guided biopsy. Although FDG is inferior to other tracers for primary staging, it may be useful in selected patients with suspected high-grade cancer. The role of ProstaScint scan is still controversial for detection of recurrent PC. This study may be helpful for evaluating nodal metastases when PSA is elevated and bone scan is negative. Bone scan remains the study of choice when bone metastases are suspected (PSA>15-20 ng/mL+/-bone pain). Acetate and choline provide better accuracy than FDG in the detection of local soft tissue disease, nodal involvement, and distant metastases. High FDG uptake may be indicative of more aggressive and possibly androgen-independent disease. PET/CT with any of the above PET tracers will most likely be preferred to the PET scan alone due to better localization of a hot lesion in PET/CT. Nuclear medicine studies also have been used to evaluate acute scrotum and testicular neoplasms. Scrotal scintigraphy has lost its popularity to Doppler ultrasound in the evaluation of the acute scrotum. In testicular tumors, FDG-PET appears to be superior to conventional imaging modalities in initial staging, detection of residual/recurrence, and monitoring treatment response. Tumor markers after treatment occasionally are elevated and cannot locate the site of recurrence, FDG-PET can play a very important role in this regard. Nuclear medicine studies also have been used to evaluate diseases of the urinary bladder. Radionuclide cystography is more sensitive and has less than 1/20 the radiation exposure of the conventional contrast enhanced micturating cystourethrogram (MCU). However, the utility of FDG-PET in the evaluation of bladder cancer seems to be limited to the evaluation of distant metastases. 11C-Methionine and choline may be a better option for local and nodal disease due to their negligible excretion in the urine.

Surveillance following radical or partial nephrectomy for renal cell carcinoma

Renal cell carcinoma (RCC) is the most lethal of the common urologic malignancies, with approximately 40% of patients eventually dying of cancer progression. Approximately one third of patients present with metastatic disease and up to 50% treated for localized disease have a recurrence. Although the prognosis generally is poor in these patients, some may respond to immunotherapy and a subset of patients who develop solitary metastases can achieve long-term survival. Therefore, the timely identification of recurrences following surgical extirpation is imperative in the treatment of patients.