A Pharmacokinetic and Pharmacodynamic Rationale for Perioperative Cancer Chemotherapy in Patients with Peritoneal Carcinomatosis

Abstract: Peritoneal carcinomatosis (PC) is a common manifestation of both gastrointestinal and gynecologic malignancies. Until recently, this condition was considered beyond curative intent treatment. Since the 1980s, new treatment strategies combining cytoreductive surgery (CRS) with perioperative intraperitoneal and intravenous chemotherapy have emerged. The underlying hypothesis considers CRS responsible for the removal of the macroscopic disease and that perioperative chemotherapy should address the residual microscopic disease. These new treatment regimens have presented encouraging clinical results that contrast with prior failure. The parameters for perioperative chemotherapy are mainly extrapolated from literature on peritoneal dialysis and data from systemic chemotherapy. The overall aim of this thesis was to provide a pharmacokinetic and pharmacodynamic rationale for perioperative intraperitoneal (IP) and intravenous (IV) chemotherapy in PC patients and, to assess its toxicity. After intraoperative IV administration of 5-fluorouracil or ifosfamide, substantial levels of these drugs were found inside the peritoneal fluid and tumor nodules (Papers I and II). This created a pharmacologically advantageous situation whereby a normothermic administered IV drug was subject to the effect of the local hyperthermia in the peritoneal fluid and tumor nodule. High levels of 5-fluouracil, ifosfamide and doxorubicin were observed inside the tumor nodules (Papers I, II and III) and, the identical pharmacokinetic advantage (expressed as Area Under the Curve (AUC) IP/IV ratios)) resulted in different drug levels of doxorubicin according to the density of the tumor nodules (Paper III). These data stressed the importance of pharmacodynamic variables such as tumor nodule density, size, and, vascularity. Therefore, the tumor nodule is proposed as a more appropriate pharmacological endpoint than AUC ratios. After IP Mitomycin C administration in PC patients with a contracted abdomen, mitomycin clearance from the abdomen decreased (Paper IV), which indicated  these patients at risk of under-treatment. Consequently, these pharmacologic data indicate a change in dosimetry for these treatment protocols might be warranted according to the diffusion area. Although diffusional vectors are viewed the main driving force for these treatment protocols, only pharmacokinetic variables such as dose, volume and duration are considered. As pharmacodynamic variables are equally important in the pharmacological assessment of cytotoxic effect, the tumor nodule was proposed as the center of a new conceptual model (Paper I). Mitomycin C data on non-metabolizers ( Paper IV) indicated the cytotoxicity of these cancer chemotherapy protocols is at the level of the individual tumor nodules. The morbidity and mortality of a new bidirectional intraoperative chemotherapy regimen in PC patients was analyzed (Paper V) which provided a means for identifying subsets of patients at risk for increased toxicity. This thesis provides pharmacokinetic and pharmacodynamic guidance for improving perioperative chemotherapy treatment strategies in PC patients and reports its toxicity.