Doctors may someday use continuous-monitoring systems for chemotherapy to keep constant track of how much of the drugs is present in the patient’s blood and automatically adjust the dose if more or less is needed, researchers say.
Similar to what’s available now for patients with diabetes who use insulin, their experimental “closed-loop” system would allow for continuous monitoring and adjusting of drug infusions to keep the dose in the so-called therapeutic range, where it’s believed to be most effective without being toxic.
Current dosing of chemotherapy drugs can be inexact and based on unreliable formulas.
In proof of concept tests in rabbits, the amount of the chemo drug 5-fluorouracil circulating in the body was analyzed every five minutes using high-performance liquid chromatography mass spectroscopy. The system kept blood levels of the drug within the target range nearly 45% of the time compared with 13% of the time in animals not using the system, according to a report published on Wednesday in Med.
The researchers performed some components of the system manually for their present experiments, however “each step could potentially be fully automated using commercially available devices, thereby enabling fully autonomous, closed-loop control of drug concentrations,” they said.
Current methods of calculating chemotherapy drug dosages, usually based on patients’ height and weight, don’t account for differences that can affect how the drug spreads through the body, or genetic variations that influence how the body uses it, the researchers said.
Furthermore, levels of enzymes that affect chemotherapy drug levels are known to fluctuate based on time of day. During the course of a single infusion, circadian rhythms can lead to tenfold fluctuations in blood levels of the commonly used drug 5-fluorouracil, the researchers said.
One patient “can have cycles of treatment with minimal toxicity and then have a cycle with miserable toxicity,” study leader Dr. Douglas Rubinson of Dana-Farber Cancer Institute in Boston said in a statement.
“Something changed in how that patient metabolized chemo from one cycle to the next. Our antiquated dosing fails to capture that change, and patients suffer as a result.”
