The surgical management of peritoneal metastases, whatever their origin, raises the problem of the potential involvement of the entire peritoneal serosa. Peritoneal metastases are surface lesions, sometimes numerous, extensive, and they may be theoretically accessible to photodynamic therapy (PDT). Intraperitoneal applications of PDT are limited by the photosensitizers lack of specificity, that should explain side effects and complications observed in the past, and by the difficulties to bring light into the cavity. Past clinical evaluations had demonstrated the risks associated with this technique (capillary leak syndrome, anastomotic leakages), and no trial evaluating PDT for peritoneal metastases treatment was published since 2006. Recent data may contribute to give a new breath for this technique. Indeed, new targeted molecules are being developed, and the optimization of illumination systems makes possible the implementation of PDT by minimally invasive approaches (laparoscopy). Immunotherapy also brings new arguments to promote PDT in this indication. Indeed, it is unrealistic to think that surgery alone can ensure satisfactory microscopic cytoreduction quality and the application of light uniformly over the whole peritoneal surface cannot be reasonably considered. Thus, the expected abscopal effect of PDT could enhance a systemic immune response leading to better control of residual lesions on the one hand, and also peritoneal and tissue recurrences at a distance. The objective of this review is to present the most recent data and possible approaches for the treatment of peritoneal carcinomatosis by PDT.

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Henri Azaïs, Martha Baydoun, Christie Rebahi, Olivier Moralès, Céline Frochot, Ludovic Colombeau, Bertrand Leroux, Elise Thécua, Nadira Delhem, Pierre Collinet, and Serge Mordon, "Treatment of peritoneal carcinomatosis of various origins by photodynamic therapy: state of the art (Conference Presentation)," Proc. SPIE 11070, 17th International Photodynamic Association World Congress, 1107026 (Presented at 17th International Photodynamic Association World Congress: June 30, 2019; Published: 14 August 2019); https://doi.org/10.1117/12.2526638.6069259391001.