Predicting Chemotherapy Success
Chemotherapy and MRI
Chemotherapy drugs, given intravenously, are the mainstay of the fight against cancer. But doctors know that sometimes these drugs effect a complete cure, while other times they can be nearly ineffective. How to turn some of those failures into successes? A team of scientists at the Weizmann Institute, headed by Prof. Hadassa Degani of the Biological Regulation Department, has come up with a non-invasive, magnetic resonance imaging- (MRI-) based method for predicting possible problems. The findings of their studies on animals, which appear today in the journal Cancer Research, may, in the future, influence treatment regimes for millions of cancer patients.
Intravenous infusions rely on the bloodstream to carry drugs to where they are needed. Normally, a material such as a chemotherapy drug crosses into a tissue on the principle of concentration equalization - the material diffuses from an area of high concentration to one of low concentration until the concentrations become equal all around. However, in some cancers, even though the material "wants" to spread out evenly, fluids inside the tumor may be exerting pressure to prevent this. When the internal pressure created by these fluids rises above a certain level, it acts as a barrier that keeps drugs and other materials from entering the tumor.
The method the Institute scientists developed can measure, with a non-invasive MRI scan, whether the fluid pressure in cancer tissues is at levels that could render chemotherapy ineffective. Their research, which led to the method, was done with MRI equipment similar to that found in hospitals and clinics. A contrast agent often employed in MRI was used as a stand-in for chemotherapy drugs, and this material was injected into special mice with different cancerous growths. The team created computer algorithms (instructions for computers) that allowed them to verify the connection between the amount of material that found its way into the growth and the pressure of the fluids inside the tumor tissue. The Weizmann Institute team's research, as well as that of other research groups, shows that this relationship can differ from one animal to the next, from one human to the next, and even from one tissue to the next in the same animal.
Prof. Degani says that, ideally, the fluid pressure inside tumor tissues would be checked using the MRI method she and her team developed before a patient begins chemotherapy. If the pressure is discovered to be high, it might be possible to reduce it by various means, such as drugs similar to those for lowering blood pressure. The method, if it proves successful in clinical trials, might have the potential to significantly increase the success rate of chemotherapy.