Third International Symposium on Focal Therapy and Imaging of Prostate and Kidney Cancer. Fairmont Hotel, Washington, DC. February 24-27, 2010.
Duke Comprehensive Care Cancer Center, Sponsor
Existing ultrasound-based technologies for treatment of prostate cancer lack accurate real-time thermal feedback during therapy, so treatment is protocol-based rather than patient-specific. Prostate motion during focal treatment is a significant issue that must be addressed. MRI-guidance (for FUS or laser therapy) continues to offer distinct advantages.
Thought leaders in urology emphasize applying focal therapy to men who truly need treatment, citing some question about the level of accurate characterization by imaging and multi-site biopsies. The option of reliable focal therapy is in fact driving the movement towards more efficient characterization. It is important to separate out those men who truly have “low risk disease” and might be managed safely by active surveillance.
Current biopsy strategies are unreliable. Greater accuracy in diagnosis (multifunctional MRI) is urgently needed. Multifunctional MRI has the grea promise in defining the relevant patient subgroups. Dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) using small molecular weight gadolinium chelates enables non-invasive imaging characterization of tissue vascularity. Depending on the technique used, data reflecting tissue perfusion, microvessel permeability surface area product, and extracellular leakage space can be obtained. Two dynamic MRI techniques (T2*-weighted or susceptibility based and T1-weighted or relaxivity enhanced methods) have shown utility for prostate carcinoma. Evidence is mounting that kinetic parameters correlate with immunohistochemical surrogates of tumor angiogenesis, including microvessel density, and with pathologic tumor grade. DCE-MRI is being applied to monitor the clinical effectiveness of a variety of treatments. Kinetic parameter changes following treatment have correlated with histopathological outcome and patient survival. Multifunctional MRI has >90% negative predictive value for 0.2 cc and 0.5 cc cancers, the commonly used thresholds for predicting quality of life and survival.
A number of groups continue to develop image-fusion i.e., registration of preoperative MR images to ultrasound-based therapeutic devices (HIFU, cryotherapy, photodynamic therapy) to deliver focal therapy. Image fusion of preoperative MRI with intra-procedural ultrasound compares poorly with real-time MRI during treatment, with significant risk of decreased efficacy and increased toxicity, and will not be seen as a preferred alternative.
Novel ultrasound techniques are unlikely to play a role in enhanced diagnosis, although they may facilitate guidance of treatment (some day). Multifunctional MR is becoming the gold standard for diagnostic precision, and therefore in fine-tuning treatment decisions (treat vs watch) and guiding focal treatment.
In terms of focal treatment of small renal masses, lesions <2.0 cm diameter need not be treated, because they are usually benign (David Albala, Duke). Lesions that should be focally treated will range from 2-5 cm in diameter (Tom Jarret, GWU). Of interest, cryoablation of renal carcinoma is usually carried 5-10 mm outside the edge of the visualized tumor, due to high recurrence rates otherwise, which adds significant volume (Bruce Shingleton, Ochsner Clinic).
The main US clinical researchers attending were Mark Emberton (University College of London), Roland van Velthoven (Brussels), Cary Robertson (Duke) and Brad Wood (NCI).