A simplified procedure for continuous intraoperative external monitoring of systemic leakage during isolated limb perfusion.

Abstract

Isolated limb perfusion (ILP) with high doses of an alkylating agent alone or in combination with tumor necrosis factor (TNF) in hyperthermic conditions (HAP) has been proposed for the treatment of locoregional tumors. A critical step in ILP/HAP is accurate monitoring of systemic leakage to prevent the toxic effects of chemotherapy, and in particular of TNF. Ten percent systemic leakage from the perfusion circuit is considered the maximum acceptable leakage. In this study we report our experience of a new leakage monitoring system. Ths new simplified procedure is based on the use of 99mTc-labeled soluble human serum albumin (HSA) and a hand-held gamma probe as detector. The procedure consists of the following steps: 1) A standardized 99mTc-HSA dose of 0.5 MBq/kg body weight is injected into the perfusion circuit before chemotherapy/TNF perfusion and a hand-held gamma probe (IGP) is placed over the precordial area in a zone that was marked on the skin during a simulation test; 2) 48-72 hours before ILP/HAP a complete simulation test is performed with a 99mTc-HSA dose corresponding to 10% of the total dose calculated for the patient's body weight; 3) during the simulation test the maximum count-rate zone on the precordial area is detected by IGP and marked on the patient's skin; 4) a 60-min curve of effective 99mTc-HSA radioactivity decay (physical and biological) is calculated and fitted; 5) to compare external counting with the effective circulating radioactivity, patient blood samples and circuit blood samples are taken every five minutes during ILP/HAP and measured by a laboratory gamma counter and very convenient thanks to the favorable characteristics of IGP. The placed in the operating room. External counting with a hand-held gamma probe was easy to perform time/activity curves obtained during simulation tests showed a regular and constant effective decay with a mean decay rate of 30% at 60 minutes compared to baseline values. The external measurements obtained by IGP proved to be well correlated with blood samples measured in vitro by a laboratory gamma counter. The results of this procedure, in particular the data of the simulation test for each patient, allowed us to correct the limit of 10% maximum leakage during ILP/HAP in accordance with the time/activity curve. Although 99mTc-HSA has some unfavorable characteristics, it offers many advantages over 131I-HSA. The procedure proposed by us, which was based on the use of an IGP and 99mTc-HAS at a standardized dose of 0.5 MBq/kg body weight and on an individual simulation test for each patient performed 48 hours before ILP/HAP, proved to be simple and accurate in monitoring systemic leakage during ILP/HAP anti-cancer therapy.