Clinical evaluation of smartphone-based fluorescence imaging for guidance and monitoring of ALA-PDT treatment of early oral cancer

Abstract

The increasing incidence of head and neck cancers in South Asia has been described as a global health crisis.¹ Particularly in India, the high incidence of oral cancers is ascribed to the popularity of chewing “gutka” (a compound mixture of tobacco, acacia, and betel nut extracts). The problem of high oral cancer incidence is exacerbated, particularly in rural areas, by limited accessibility of early stage medical screening and imaging. Furthermore, the economic burden of late stage treatments such as complex surgical procedures and/or radiation therapy pose a further barrier in oral cancer management.² Photodynamic therapy (PDT) has emerged as an alternative and noninvasive early stage anticancer treatment modality.³ PDT is a treatment in which a precursor or photosensitizer drug localized to the lesion sites is activated by light to generate singlet oxygen (${}^1{\mathrm{O}}_2$)-mediated photocytotoxicity against cancer cells. Here, we used 5-aminolevulinic acid (ALA as Levulan^®, DUSA, SUN Pharmaceuticals, Inc.), a precursor for the photoactive derivative protoporphyrin IX (PpIX).⁴ PpIX not only acts as a fluorescent probe but also imparts antitumor toxicity when activated by light. This dual functionality has been used successfully for image-guided treatment of various cancers, including those of the oral cavity.^5,6 In clinical settings, PpIX fluorescence and photobleaching make it effective as a diagnostic as well as a treatment monitoring tool.^7,8 Recently, a smartphone with fluorescence imaging capability has been used as a low-cost device for premalignant oral screening.⁸ The wide availability and popularity of smartphones, particularly in the developing countries, make this device promising as a low-cost, portable, and capable theragnostic cancer technology for global health.^{9 – 11} Building on previous preliminary findings,¹² we report here an evaluation of this simple and low-cost fluorescence imaging approach for guidance and monitoring of PDT treatment in the clinic.