Monitoring tissue temperature during photothermal therapy for cancer

Abstract

Phototherapies offer promising alternatives to traditional cancer therapies. Phototherapies mainly rely on manipulation of target tissue through photothermal, photochemical, or photomechanical interactions. Combining phototherapy with immunotherapy has the benefit of eliciting a systemic immune response. Specifically, photothermal therapy (PTT) has been shown to induce apoptosis and necrosis in cancer cells, releasing tumor associated antigenic peptides while sparing healthy host cells, through temperature increase in targeted tissue. However, the tissue temperature must be monitored and controlled to minimize adverse thermal effects on normal tissue and to avoid the destruction of tumor-specific antigens, in order to achieve the desired therapeutic effects of PTT. Techniques for monitoring PTT have evolved from post-treatment quantification methods like enzyme linked immunosorbent assay, western blot analysis, and flow cytometry to modern methods capable of real-time monitoring, such as magnetic resonance thermometry, computed tomography, and photoacoustic imaging. Monitoring methods are largely chosen based on the type of light delivery to the target tissue. Interstitial methods of thermometry, such as thermocouples and fiber-optic sensors, are able to monitor temperature of the local tumor environment. However, these methods can be challenging if the phototherapy itself is interstitially administered. Increasingly, non-invasive therapies call for non-invasive monitoring, which can be achieved through magnetic resonance thermometry, computed tomography, and photoacoustic imaging techniques. The purpose of this review is to introduce the feasible methods used to monitor tissue temperature during PTT. The descriptions of different techniques and the measurement examples can help the researchers and practitioners when using therapeutic PTT.

Thermoplasmonics with Gold Nanoparticles: A New Weapon in Modern Optics and Biomedicine

“…The extraordinary ability to detect passive IR radiation makes thermal imaging cameras an indispensable tool in thermometry. [ 54 ] It is, however, important to keep in mind that, in the thermographic‐based analysis, the emittance of the object is a parameter that has to be taken into account (the emittance of a surface is defined as the ratio of radiation flux per unit area of a blackbody radiator's emitter at the same temperature and under the same conditions). [ 55 ]…”

Ag2S Nanoheaters with Multiparameter Sensing for Reliable Thermal Feedback during In Vivo Tumor Therapy

“…[10][11][12][13] This, in turn, allows the avoidance of both insufficient and overheating ranges, which could lead to either inefficient therapy or to excessive collateral damage, respectively. [14] As both heating and thermal readings are triggered by a single laser beam, such control could lead to simple and cost effective photothermal treatments. Several examples do exist in the literature demonstrating successful thermal in vivo treatment of tumors with S-MPThs, based on either lanthanide-doped NPs or infrared-emitting quantum dots (QDs).…”

“…[ 3 ] This, in turn, avoids the extremes of having either insufficient or excessive heating, which could lead to either inefficient therapy or collateral damage, respectively. [ 4 ] The importance of intratumoral temperature monitoring is such that the Food and Drug Administration (FDA) has launched safety warnings in already approved thermal therapy devices. When using S‐MPThs both heating and luminescence‐based thermal readings are triggered by a single laser beam, so that intratumoral heating and thermal sensing could be achieved straightforwardly.…”

PhotoPhage: A Virus-based Photothermal Therapeutic Agent

“…[4][5][6] Typically, to achieve an efficient thermal ablation in the tumor microenvironment (TME), heating over 50 °C is required. 7 The induced inflammation kills cancer cells by impairing protein and DNA function in addition to turning "cold" immune-dysfunctional TMEs into "hot" immunological environments by stimulating the production and release of DAMPs that prime the formation of activated dendritic cells and promote the production of cancer killing CD8+ T-cells. [8][9] However, there is accumulating evidence that not only the induced immunological response from thermal ablation is not strong enough on its own to inhibit tumor growth at distant sites, but the release of DAMPs followed by inflammation may actually promote development and progression of tumors by inducing propagation of local immunosuppressive regulatory T (Treg) cells and myeloid derived suppressor cells (MDSC).…”