Thermal analysis of laser irradiation-gold nanorod combinations at 808 nm, 940 nm, 975 nm and 1064 nm wavelengths in breast cancer model

Background

Photothermal therapy is currently under the spotlight to improve the efficacy of minimally invasive thermal treatment of solid tumors. The interplay of several factors including the radiation wavelengths and the nanoparticle characteristics underlie the thermal outcome. However, a quantitative thermal analysis in in vivo models embedding nanoparticles and under different near-infrared (NIR) wavelengths is missing.

Purpose

We evaluate the thermal effects induced by different combinations of NIR laser wavelengths and gold nanorods (GNRs) in breast cancer tumor models in mice.

Materials and methods

Four laser wavelengths within the therapeutic window, i.e., 808, 940, 975, and 1064 nm were employed, and corresponding GNRs were intratumorally injected. The tissue thermal response was evaluated in terms of temperature profile and time constants, considering the step response of a first-order system as a model.

Results

The 808 nm and 1064 nm lasers experienced the highest temperature enhancements (>24%) in presence of GNRs compared to controls; conversely, 975 nm and 940 nm lasers showed high temperatures in controls due to significant tissue absorption and the lowest temperature difference with and without GNRs (temperature enhancement <10%). The presence of GNRs resulted in small time constants, thus quicker laser-induced thermal response (from 67 s to 33 s at 808 nm).

Conclusions

The thermal responses of different GNR-laser wavelength combinations quantitatively validate the widespread usage of 808 nm laser for nanoparticle-assisted photothermal procedures. Moreover, our results provide insights on other usable wavelengths, toward the identification of an effective photothermal treatment strategy for the removal of focal malignancies.

Laser interstitial thermotherapy (LITT) for breast cancer: dosimetry optimization and numerical simulation

Surgical treatment is standard for the treatment of small breast cancers. Due to the pain and esthetic sequelae that can follow surgery, minimally invasive treatments are under investigation. Our aim was to conduct a dosimetry study of laser interstitial thermotherapy. Turkey tissue was used as an ex vivo model, and mammary glands from ewes were used as in vivo models. We used two different wavelength lasers (805 nm and 980 nm). Two types of fiber from two different manufacturers were used: bare fibers with a diameter of 600 μm and diffusing fiber. The diffusing fibers were 5 mm and 10 mm in length. We also used a computerized model to predict thermal damage and to correlate with the ex vivo and in vivo procedures using a constant and variable coefficient. The mathematical model was based on the finite element method for solving light distribution, bio-heat, and thermal damage equations. Based on our ex vivo and in vivo experiments, we found that the optimal configuration for this treatment was the use of the 980-nm laser at 4 W with bare fibers for a minimum treatment time of 150 s. We also developed a predictive mathematical model that showed good predictability of necrosis in line with the experimental data. Laser treatment is a promising therapy for small breast lesions. However, further development of treatment guidance is necessary to support its use in clinical practice.

Effect of optical energy modulation on the thermal response of biological tissue: computational and experimental validations

This study develops an energy modulation technique to attain a constant interstitial tissue temperature and to induce the predetermined thermal coagulation without carbonization in tissue. An optical diffuser was employed to deliver 1064 nm light to the biological tissue. The combined mode maintained the interstitial temperature at 70 °C for longer durations compared to the continuous wave mode. Coagulation volumes increased linearly with the time and met the predetermined treatment volume range (0.32-0.52 cm³) after the combined treatment for 100 s. The combined modulation can be a feasible modality to induce the predetermined extent of thermal coagulation for treating papillary thyroid microcarcinoma.

The prostate cancer focal therapy

Despite prostate cancer (PCa) is the leading form of non-cutaneous cancer in men, most patients with PCa die with disease rather than of the disease. Therefore, the risk of overtreatment should be considered by clinicians who have to distinguish between patients with high risk PCa (who would benefit from radical treatment) and patients who may be managed more conservatively, such as through active surveillance or emerging focal therapy (FT). The aim of FT is to eradicate clinically significant disease while protecting key genito-urinary structures and function from injury. While effectiveness studies comparing FT with conventional care options are still lacking, the rationale supporting FT relies on evidence-based advances such as the understanding of the index lesion's central role in the natural history of the PCa and the improvement of multiparametric magnetic resonance imaging (mpMRI) in the detection and risk stratification of PCa. In this literature review, we want to highlight the rationale for FT in PCa management and the current evidence on patient eligibility. Furthermore, we summarize the best imaging modalities to localize the target lesion, describe the current FT techniques in PCa, provide an update on their oncological outcomes and highlight trends for future research.

Targeted Ablative Therapies for Prostate Cancer

Men diagnosed with low- to intermediate-risk, clinically localized prostate cancer (PCa) often face a daunting and difficult decision with respect to treatment: active surveillance (AS) or radical therapy. This decision is further confounded by the fact that many of these men diagnosed, by an elevated PSA, will have indolent disease and never require intervention. Radical treatments, including radical prostatectomy and whole-gland radiation, offer greater certainty for cancer control, but at the risk of significant urinary and/or sexual morbidity. Conversely, AS preserves genitourinary function and quality of life in exchange for burdensome surveillance and the psychological impact of living with cancer.

[Indications and limits of ablative therapies in prostate cancer]

OBJECTIVE

To perform a state of the art about indications and limits of ablative therapies for localized prostate cancer.

METHODS

A review of the scientific literature was performed in Medline database (http://www.ncbi.nlm.nih.gov) and Embase (http://www.embase.com) using different associations of keywords. Publications obtained were selected based on methodology, language and relevance. After selection, 107 articles were analysed.

RESULTS

The objective to combine reduction of side effects and oncological control has induced recent development of several ablative therapies. Beyond this heterogeneity, some preferential indications appear: unilateral cancer of low risk (but with significant volume, excluding active surveillance) or intermediate risk (excluding majority of grade 4); treatment targeted the index lesion, by quarter or hemi-ablation, based on biopsy and mpMRI. In addition, indications must considered specific limits of each energy, such as gland volume and tumor localization.

CONCLUSION

Based on new imaging and biopsy, ablative therapies will probably increased its role in the future in management of localize prostate cancer. The multiple ongoing trials will certainly be helpful to better define their indications and limits.

Laser interstitial thermotherapy application for breast surgery: Current situation and new trends

While breast specialists debate on therapeutic de-escalation in breast cancer, the treatment of benign lesions is also discussed in relation to new percutaneous ablation techniques. The purpose of these innovations is to minimize potential morbidity. Laser Interstitial ThermoTherapy (LITT) is an option for the ablation of targeted nodules. This review evaluated the scientific publications investigating the LITT approach in malignant and benign breast disease. Three preclinical studies and eight clinical studies (2 studies including fibroadenomas and 6 studies including breast cancers) were reviewed. Although the feasibility and safety of LITT have been confirmed in a phase I trial, heterogeneous inclusion criteria and methods seem to be the main reason for LITT not being yet an extensively used treatment option. In conclusion, further development is necessary before this technique can be used in daily practice.

In-bore MRI interventions: current status and future applications

PURPOSE OF REVIEW

This review discusses the feasibility, recent advances and current status of in-bore MRI-guided interventional techniques for diagnosis and treatment of focal prostate cancer (PCa) and also explores the future applications, highlighting the emerging strategies for the treatment of PCa.

RECENT FINDINGS

Multiparametric MRI has opened up opportunities for diagnosis and targeted therapeutics to the site of disease within the organ wherein minimizing the incidence of treatment-related toxicity of whole gland therapy. MRI-guided targeted biopsy has a higher detection rate for significant cancer and lower rate of detection of insignificant cancer. In comparison to ultrasound-guided focal therapy, in-bore treatment provides the advantage of real time thermal monitoring during treatment and assessment of treatment coverage by an enhanced scan immediately post-treatment. Preliminary results of ongoing phase I and II in-bore focal PCa treatment trials via transperineal, transrectal and transurethral routes, using different energy modalities for the ablation, have shown promising results.

SUMMARY

Advances in multiparametric-MRI has opened up opportunities for in-bore targeted focal treatment of PCa in the correctly selected patient.

Photothermal cancer therapy by gold-ferrite nanocomposite and near-infrared laser in animal model

Surface plasmon resonance effect of gold nanostructures makes them good candidates for photothermal therapy (PTT) application. Herein, gold-ferrite nanocomposite (GFNC) was synthesized and characterized as a photothermal agent in PTT. The aim of this study was to investigate the effect of GFNC upon laser irradiation on treatment of cancer in mice bearing melanoma cancer. Thirty mice received 1.5 × 10(6) B16/F10 cells subcutaneously. After 1 week, the mice bearing solid tumor were divided into four groups: control group (without any treatment), laser group (received laser irradiation without GFNC injection), GFNC group (only received intratumorally GFNC), and GFNC + laser group (received intratumorally GFNC upon laser irradiation). In GFNC + laser group, 200 μL of fluid, 1.3 × 10(-7) mol L(-1) gold nanoparticles, was injected intratumorally and immediately the site of tumor was exposed to continuous wave diode laser beam (808 nm, 1.6 W cm(-2)) for 15 min. All mice but four were euthanized 24 h after treatment to compare the necrotic surface area histologically by using measuring graticule. Statistical analyses revealed significant differences in necrosis extent for GFNC + laser group, compared to other groups. Four subjects (control group and GFNC + laser group, two mice each) were kept for longitudinal study. Histological analyses and tumor volume measurements of the four subjects indicated that tumor in GFNC + laser group was controlled appropriately. It was concluded that combining an 808-nm laser at a power density of 1.6 W cm(-2) with GFNC has a destruction effect in melanoma cancer cells in an animal model.

MRI-guided biopsies and minimally invasive therapy for prostate cancer

Recent advances in multiparametric magnetic resonance imaging (mp-MRI) have led to a paradigm shift in the diagnosis and management of prostate cancer (PCa). Its sensitivity in detecting clinically significant cancer and the ability to localize the tumor within the prostate gland has opened up discussion on targeted diagnosis and therapy in PCa. Use of mp-MRI in conjunction with prostate-specific antigen followed by targeted biopsy allows for a better diagnostic pathway than transrectal ultrasound (TRUS) biopsy and improves the diagnosis of PCa. Improved detection of PCa by mp-MRI has also opened up opportunities for focal therapy within the organ while reducing the incidence of side-effects associated with the radical treatment methods for PCa. This review discusses the evidence and techniques for in-bore MRI-guided prostate biopsy and provides an update on the status of MRI-guided targeted focal therapy in PCa.

Laser ablation as focal therapy for prostate cancer

PURPOSE OF REVIEW

Focal laser ablation (FLA) is an emerging treatment paradigm for prostate cancer that aims to successfully eradicate disease while also reducing the risk of side-effects compared with whole-gland therapies.

RECENT FINDINGS

Preclinical and phase I clinical trials for low-risk prostate cancer have shown that FLA produces accurate, predictable, and reproducible ablation zones with negligible injury to the surrounding tissues. Because FLA is magnetic resonance compatible, the procedure can be monitored with real-time feedback to optimize targeted treatment of cancerous foci and minimize quality-of-life side-effects. The oncologic efficacy of MRI-guided FLA is currently being evaluated in ongoing phase II clinical trials.

SUMMARY

FLA is a well tolerated and feasible therapy for low-risk prostate cancer, and the oncologic efficacy of this treatment modality is currently under investigation in phase II clinical trials at several institutions.

An anatomically realistic and adaptable prostate phantom for laser thermotherapy treatment planning

PURPOSE

To construct a phantom for prostate cancer laser based thermotherapy treatment planning and simulation.

METHODS

A realistic and adaptable prostate phantom was designed. It exhibits the following properties: valid and complete description of the prostate anatomy, material with similar optical properties of prostate tissues and compatibility with clinical imaging protocols mainly multiparametric magnetic resonance (MR) and transrectal ultrasound imaging (TRUS).

RESULTS

Preliminary experiments with the phantom using an interstitial laser treatment protocol allowed obtaining results similar to those obtained on preclinical model.

CONCLUSIONS

These results proved that this phantom could allow a real simulation of laser therapy procedure: target definition and fibers' placement optimization using MR imaging, treatment delivery, and finally treatment monitoring using TRUS imaging.

Efficiency of 5-ALA mediated photodynamic therapy on hypoxic prostate cancer: a preclinical study on the Dunning R3327-AT2 rat tumor model

OBJECTIVES

To evaluate photodynamic therapy (PDT) using 5-ALA-induced protoporphyrin IX (PPIX) in an in vivo hypoxic tumor model and its monitoring using MRI.

MATERIAL AND METHODS

Dunning R3327-AT2 tumors were grafted in the neck of Copenhagen rats. PDT using 150 mg 5-ALA/kg i.v. was performed by focal interstitial illumination of the photosensitized tumor (λ=633 nm; fluence=100 J/cm(2)). MRI at baseline and 2 days after treatment (T1, T2 and dynamic gadolinium enhanced sequences) were performed. Necrosis volumes were determined on post-procedure MRI. Tumors were resected 2 days post-PDT and obtained necrosis was determined histopathologically. Intra-tumoral PPIX distribution was evaluated using confocal microscopy and tissue porphyrin quantification.

RESULTS

Twenty rats were treated divided into three groups: continuous (n=7), fractionated illumination (n=7), and a control group receiving only light or only ALA or neither (n=6). Baseline MRI confirmed the hypoxic character of tumors. Necrosis volumes determined on posttreatment MRI were not reproducible and presented with important geometric and volumetric variability. Average necrosis volumes of 0.39 cc (0-0.874 cc) in the continuous group, 0.24 cc (0.107-0.436 cc) in the fractionated group and 0.012 cc (0-0.071 cc) in the control group were observed. Intra-tumoral PPIX distribution was heterogeneous and PPIX quantification revealed low intra-tumoral concentration.

CONCLUSION

Necrosis volumes induced by 5-ALA-mediated PDT were highly variable and non reproducible, probably because of lack of intra-tissular oxygen. Photosensitizer was poorly represented inside the tumor and its distribution was heterogeneous. Our study suggests that 5-ALA-mediated PDT might not be the best management option for hypoxic prostatic adenocarcinoma.

Laser interstitial thermotherapy of small breast fibroadenomas: numerical simulations

BACKGROUND

Laser interstitial thermotherapy (LITT) is potentially a novel method to treat small breast fibroadenoma, without the need for surgical removal. Dosimetry planning and conformation of the treated area of tumor remain major issues, especially for a moving organ such as the breast. Pre-treatment simulation planning of this therapy is an effective method to predict the final thermal damage. In this study, a mathematical model is elaborated to simulate the heat distribution and the thermal damage.

METHODS

The mathematical model was based on finite element method (FEM) to solve the light distribution, bioheat, and thermal damage equations. Six simulations were performed with the following powers: 5, 6, 7, 8, 9, and 10 W (λ = 980 nm), and for an irradiation time of 125 seconds, with a 50 °C iso-damage temperature. To validate these simulations, six turkey breast samples were irradiated with parameters used for simulations. Volumes of thermal damage were calculated by using formulas: spherical, Elliptical, and Carlsson volumes and compared to the simulated volumes.

RESULTS

Differences between volumes were from 0.01 to 1 cm3. Interpolations between volumes from ex vivo experiments with corresponding powers were established. The relationship between the volume of the thermal damage and the laser power was described by a polynomial equation (R2  = 0.99). The power estimated by the interpolation to obtain 1 cm3 of thermal damage was 7.4 W (922 J) and the maximum corresponding temperature was 90 °C.

CONCLUSION

In this study, a good correlation was established between simulation and ex vivo experiments of LITT for fibroadenoma breast cancer.

Focal laser ablation of prostate cancer: definition, needs, and future

Current challenges and innovations in prostate cancer management concern the development of focal therapies that allow the treatment of only the cancer areas sparing the rest of the gland to minimize the potential morbidity. Among these techniques, focal laser ablation (FLA) appears as a potential candidate to reach the goal of focusing energy delivery on the identified targets. The aim of this study is to perform an up-to-date review of this new therapeutic modality. Relevant literature was identified using MEDLINE database with no language restrictions (entries: focal therapy, laser interstitial thermotherapy, prostate cancer, FLA) and by cross-referencing from previously identified studies. Precision, real-time monitoring, MRI compatibility, and low cost of integrated system are principal advantages of FLA. Feasibility and safety of this technique have been reported in phase I assays. FLA might eventually prove to be a middle ground between active surveillance and radical treatment. In conclusion, FLA may have found a role in the management of prostate cancer. However, further trials are required to demonstrate the oncologic effectiveness in the long term.

Focal laser ablation of prostate cancer: numerical simulation of temperature and damage distribution

Background

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. 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.

Methods

The 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.

Results

The 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°.

Conclusions

In 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.