Treatment of Walker ascites tumor cells by combination of photodynamic therapy with cyclophosphamide and interleukin-2 entrapped in liposomes

The purpose of this study was to investigate the beneficial and adverse local effects of PDT associated with chemoimmunotherapy on rats bearing Walker ascites tumor cells. Experiments were performed on five batches of Wistar inbred rats with ascites tumor cells receiving intraperitoneally PDT (Photofrin II and 18 hrs later HeNe laser irradiation); Cyclophosphamide (CY); interleukin-2 (IL-2) or associated therapy (PDT+CY+IL-2). The control batch consisted of untreated rats (HBSS). The following results were noticed: (a) sole administration of PDT, IL-2 or CY reduced tumor growth, gave survival rates between 28.4 and 56.5% and cure rates ranging from 12.4 to 33.3%; (b) combined therapy (PDT+CY+IL-2) decreased tumor growth, increased survival rates (88.5%) and cure rates were 73.1% forty-two days post-transplantation. Summing up, in this study we noticed that PDT associated with chemoimmunotherapy reduced mortality as well as tumor volumes and increased cure rates in rats with ascites tumor cells. This approach points to the need for further evaluation in patients with peritoneal malignancies.