This volume provides a comprehensive review of resistance induced by photodynamic therapy (PDT)
in tumor cells. Understanding the underlying mechanisms in this process leads to the
improvement of therapeutic modality in combination with chemotherapy immunotherapy and
radiotherapy. Photodynamic therapy is a minimally invasive therapeutic procedure that can exert
a selective or preferential cytotoxic activity toward malignant cells. The procedure involves
administration of an intrinsically non-toxic photosensitizing agent (PS) followed by
irradiation at a wavelength corresponding to a visible absorption band of the sensitizer. In
the presence of oxygen a series of events lead to direct tumor cell death damage to the
microvasculature and induction of a local inflammatory reaction. Studies reveal that PDT can
be curative particularly in early stage tumors and this volume explores the potential of PDT
but also reveals strategic approaches to overcome resistance in tumor cells.
