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12LIGHT AND ULTRASOUND TO TREAT IN A NON-INVASIVE WAY NODULAR AND PIGMENTED SKIN
LESIONS
ERIKA TONETH PONCE AYALA, MURILO DE OLIVEIRA SOUZA, CAMILA APARECIDA ANTUNES, MARLON RODRIGUES GARCIA, MICHELLE BARRETO REQUENA, FERNANDA ALVES DIAS DE SOUSA, LILIAN TAN MORIYAMA, CRISTINA KURACHI, ANA GABRIELA SALVIO, VANDERLEI SALVADOR BAGNATO, SEBASTIAO PRATAVIEIRA
Sao Carlos Institute of Physics, University of Sao Paulo
ABSTRACT
Despite all the efforts and scientific-technological advances in recent years, deaths from any types of cancer are still among the top 3 causes of death in the world. Among the factors for this, we can mention the increase in life expectancy, the growth in the world population, and exposure to carcinogens. Nevertheless, lack of medical assistance is also aggravating for these deaths.
In BRICS countries with large populations and few resources, it is extremely necessary to develop efficient and low-cost treatments to be widely adopted. For example, some types of skin lesions, such as pigmented lesions, nodular lesions, and especially melanoma, are a relevant health problem due to the difficulty in treating them in a non-invasive and painless way. The standard treatment for these types of injuries is surgical resection, however, it is very invasive and aggressive, and the aesthetic result is poor. Therefore, several treatment possibilities are being developed and tested to change this clinical reality. One option is Photodynamic Therapy, which has proven to be very efficient for treating superficial non-melanoma skin lesions. In these cases, PDT is a non-invasive procedure and uses a combination of light, a light-sensitive drug - called a photosensitizer (FS), and molecular oxygen (O2), after the interaction of these three ingredients, reactive oxygen species are generated resulting in cell death. This technique has been successfully implemented in Brazil and worldwide, with efficient, safe, and better aesthetic results in comparison with other used methods.
However, there are still lesions that need alternative methods to the current ones, such as nodular and pigmented lesions where the delivery of light in a non-invasive way is a challenge, due to the light-tissue interaction properties, the light penetration necessary to initiate the photodynamic effect is limited to a few millimeters. An alternative method to overcome these challenges is the sonodynamic therapy (TSD), which consists of using low frequency ultrasound waves (US) and now a molecule that is activated by ultrasound - a sonosensitizer (SS). SDT has an application protocol like PDT, in which the SS applied to the patient interacts with the US waves leading to cell death. Unlike light, US easily crosses biological tissues due to its low attenuation, which allows this therapy to reach deeper tumors.
In this talk, we will present study that aims to evaluate the ability of 5-aminolevulinic acid (5-ALA) mediated SPDT to reduce the size of B16-F10 melanoma tumors in mice. B16-F10 tumor cells (1x106 cells) were implanted subcutaneously on the right-side flanks of nude mice. When the tumor reached an average volume of ~100mm3, mice were treated with 1 daily session of PDT, SDT or SPDT for 5 days. Mice were intraperitoneally injected with 5-ALA at the dose of 250 mg/kg weight, after 3h of injection, mice were irradiated with light (red laser, 100 mW/cm2), ultrasound (1MHz, 1.5 W/cm2, 20,50 %) and both sources. For these procedures, a single probe capable of irradiating light and ultrasound individually and simultaneously was developed. Tumor volume was measured at the time of each treatment and daily after the treatment for 6 days. Tissue sections will be analyzed through histological processing.
It was observed in SDT group, a decrease in tumor size after the first session as well as in tumor growth rate after treatment. Results obtained so far (SDT group) suggest that the combination of SDT and PDT can improve the effectiveness of each treatment applied individually. The combination of PDT and SDT could be very useful noninvasive technique for treatment of melanoma skin cancer.
