Intraperitoneal photodynamic therapy

Peritoneal carcinomatosis and sarcomatosis are generally incurable problems for which there are few good treatment options. Intraperitoneal PDT is potentially an ideal therapy for peritoneal carcinomatosis because of its relatively superficial treatment effect. A Phase II trial of IP PDT with the first generation photosensitizer, Photofrin, demonstrates that this treatment approach is tolerable clinically but is associated with substantial toxicity suggesting a narrow therapeutic index. Remarkably, responses were observed in heavily pre-treated patients suggesting clinical activity. Correlative studies of photosensitizer uptake in human tumour and normal tissues show little tumour selectivity. This lack of photosensitizer selectivity for tumour in combination with tumour hypoxia (as opposed to oxic normal tissues) is likely a major reason for the narrow therapeutic index of intraperitoneal PDT. However, the advent of novel and potentially molecularly targeted photosensitizers, combined with enhancement of PDT cancer cell cytotoxicity through inhibition of growth factor signaling should greatly improve the therapeutic index of intraperitoneal PDT. In addition, other approaches, including the use of nanotechnology, may allow the administration of fractionated PDT which may also improve the therapeutic index of this treatment. The clinical implementation of these technologies may allow for highly effective and well tolerated treatment of intraperitoneal carcinomatosis with PDT.