Abstract
BackgroundThe use of minimally invasive ablative techniques in the management of patients with low grade and localized prostate tumours could represent a treatment option between active surveillance and radical therapy. Focal laser ablation (FLA) could be one of these treatment modalities. Dosimetry planning and conformation of the treated area to the tumor remain major issues, especially when, several fibers are required. An effective method to perform pre-treatment planning of this therapy is computer simulation. In this study we present an in vivo validation of a mathematical model.MethodsThe simulation model is based on finite elements method (FEM) to solve the bio-heat and the thermal damage equations. Laser irradiation was performed with a 980 nm laser diode system (5 W, 75 s). Light was transmitted using a cylindrical diffusing fiber inserted inside a preclinical animal prostate cancer model induced in Copenhagen rats. Non-enhanced T2-weighted and dynamic gadolinium-enhanced T1-weighted MR imaging examinations were performed at baseline and 48 hours after the procedure. The model was validated by comparing the simulated necrosis volume to the results obtained in vivo on (MRI) and by histological analysis. 3 iso-damage temperatures were considered 43° C, 45° C and 50° C.ResultsThe mean volume of the tissue necrosis, estimated from the histological analyses was 0.974 ± 0.059 cc and 0.98 ± 0.052 cc on the 48 h MR images. For the simulation model, volumes were: 1.38 cc when T = 43° C, 1.1 cc for T = 45°C and 0.99 cc when T = 50 C°.ConclusionsIn this study, a clear correlation was established between simulation and in vivo experiments of FLA for prostate cancer.Simulation is a promising planning technique for this therapy. It needs further more evaluation to allow to FLA to become a widely applied surgical method.
Highlights
The use of minimally invasive ablative techniques in the management of patients with low grade and localized prostate tumours could represent a treatment option between active surveillance and radical therapy
Current therapeutic recommendations for localized prostate cancer consist in radical options aiming to treat the prostatic gland in its totality
The precise evaluation of the optical parameters of prostate tissue remains a challenging issue and all reported studies confirmed that they are heterogeneous and their integration in a modeling process remains difficult and imprecise. For these reasons we considered that the Qabs term corresponds to the heat source and a constant value of 5 W.mm-3 was fixed in the model
Summary
The use of minimally invasive ablative techniques in the management of patients with low grade and localized prostate tumours could represent a treatment option between active surveillance and radical therapy. A 0.5 cc volume threshold is currently accepted to define a lesion with clinically-significant size. This volume is associated with a 10% risk of extra-capsular extension and metastasis [5]. Current therapeutic recommendations for localized prostate cancer consist in radical options aiming to treat the prostatic gland in its totality (radical prostatectomy, radiotherapy, brachytherapy, or HIFU). The use of minimally invasive ablative techniques in the management of patients with low grade and localized tumours could represent a treatment option between active surveillance and radical therapy. Based on the use of low-power laser, which delivers luminous energy using an adapted optical system, FLA produces a coagulation necrosis zone, which volume can be controlled, reducing the risk of damage to healthy adjacent structures
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