Review of mechanisms and recent advances in cancer photo thermal therapy

Abstract. Cancer is a major health problem all over the world. Photo thermal therapy (PTT) is a non-invasive method in cancer treatment. In PTT, the laser light usually in near-infra red region is absorbed and converted to heat in the cancerous tissue. The temperature above 40 ° C in PTT can induce some effects including irreversible damage to proteins, changes in enzyme structures, failed dual DNA repair, and lack of glucose. Low thermal threshold, low pH, and hypoxia condition of cancer cells can be exploited for PTT. But the remaining challenges facing researchers in cancer treatment are limited access, treatment resistant property, cancer metastasis and recurrence as well as normal cell damages. The purpose of this paper is to evaluate the PTT mechanisms and review the novel approaches of PTT in cancer treatment. In last decade, the PTT efficacy has been increased due to recent advances in nanotechnology. Use of nanoparticles (NPs) such as carbon-based NPs, metal NPs (e.g. gold, iron, and palladium) intensifies PTT efficacy due to surface plasmon resonance (SPR) property. Using SPR property and therefore improving the treatment efficiency, less intensive laser can be used for PTT. Therefore, concern about damage to normal cells has been considerably addressed. PTT based on NPs also can reduce the limited access in conventional PTT. Owing to enhanced permeability and retention effect of the NPs in tumors, tumors that are deeper than 3-5 cm can be treated efficiently. Using a proper active targeting of NPs for PTT, we can selectively target the cancer cells including the metastatic ones. PTT in accompany with the NPs can generate intense and sub-cellular localized heat in abnormal cells; therefore, the tumors resistance to PTT have been diminished thorough combination of PTT and chemo/radiotherapy.  In conclusion, based recent advances especially in nanotechnology, PTT is a simple & non-invasive treatment that can provide a better output, and can reduce the costs, side effects, and other limitations in cancer treatment.