Pharmacokinetic and phase II study of heated intraoperative intraperitoneal melphalan.

Background: Peritoneal surface malignancy resulting from local dissemination is a common manifestation of treatment failure of gastrointestinal cancers. Although the management of carcinomatosis has been improved with an aggressive surgical approach of extensive cytoreduction followed by heated intraoperative intraperitoneal chemotherapy, no patients are cured when there is residual disease after surgery. Melphalan (L-phenylalanine mustard) is a well-known antineoplastic alkylating agent which has markedly increased pharmacological activity with heat. The use of heated intraoperative intraperitoneal melphalan may provide a pharmacokinetic and clinical advantage in this group of gastrointestinal cancer patients who cannot be made cancer-free with cytoreductive surgery.

Methods: Thirteen patients with residual disease following cytoreductive surgery for peritoneal carcinomatosis were included in this study. After surgical resection and prior to anastomotic reconstruction, patients received intraperitoneal melphalan (70 mg/m2) in 3 l of 1.5% dextrose peritoneal dialysis solution at 41-42 degrees C for 90 min. Concentrations of melphalan were assessed in the peritoneal fluid, blood, urine and tumor nodules using high-performance liquid chromatography.

Results: During the 90 min of treatment 87.2 +/- 4.3% of the drug was absorbed from the perfusate/peritoneal fluid and 11.9 +/- 2.1% was excreted in the urine. The area-under-the-curve ratio of peritoneal fluid to plasma was 33.3 +/- 11.8 with an average peak plasma concentration of 0.82 +/- 0.24 microg/ml occurring at 28.5 +/- 13.1 min. Concentrations of melphalan in tumor nodules on the peritoneal surface were approximately ten times higher than in plasma with an average peak concentration of 7.2 +/- 4.2 microg/gm. The grade III/IV morbidity was 38%; there was no mortality.

Conclusion: Approximately 90% of the drug was absorbed during the 90-minute procedure with a 30 times greater exposure of drug at the peritoneal surfaces than in the blood. Concentrations of the drug in peritoneal surface tumor nodules were approximately ten times greater than concentrations in the blood. These data demonstrate that heated intraoperative intraperitoneal melphalan could have a significant impact on the treatment of peritoneal surface malignancies.