Scientists have determined that a magnetic resonance imaging (MRI) technique, which measures the movement of water molecules within the tumor, may be the best way to track how women with late-stage ovarian cancer are responding to treatment.

The study was published online February 13, 2012, in the journal Radiology. Researchers from the Cambridge Experimental Cancer Medicine Centre at the University of Cambridge (UK) compared three diverse MRI techniques and showed that a type called diffusion-weighted MRI. MRI is the most effective at indicating response to treatment and also at distinguishing when tumors that had spread from the ovaries into surrounding tissues were not responding.

Computed tomography (CT) scans are typically used to help evaluate whether ovarian cancer patients should continue having chemotherapy after their first round of treatment, but can only detect differences in the size of the tumor as opposed to a change in its structure.

Study leader Dr. Evis Sala, from the University of Cambridge, said, “At the moment we rely on CT scans and blood tests to tell us what’s going on inside a patient’s tumor. But it’s difficult to judge how effective treatment has been from these alone, particularly when the cancer has spread to other tissues where it may behave differently to the primary tumor. We’ve shown that diffusion-weighted MRI can give a much better idea of the density of tumors, in addition to their size, making it easier to determine which patients are benefitting most from the treatment. We are now collaborating on a nationwide study to see if this type of imaging could be an effective way of predicting treatment response in a much larger group of patients with advanced ovarian cancer.”

Each patient underwent an MRI of the abdomen and pelvis, including three additional MRI techniques on top of the conventional scans. The different imaging techniques were compared using various parameters--one called apparent diffusion coefficient (ADC) measures the movement of water molecules in tumors.

The researchers compared the ADC measurements in the primary tumor and in cancer cells that had metastasized from the ovaries into lining of the abdomen. They discovered there was a larger increase in the ADC of the primary tumor among those who responded to treatment compared to those who did not; while in the sites of cancer spread, there was no change.

Senior author Dr. James Brenton from Cancer Research UK’s Cambridge Research Institute, added, “The increase in ADC seen in the primary tumor in patients who responded to treatment is due to the chemotherapy killing some of the cancer cells, which in turn increases the amount of space inside the tumor allowing water molecules to flow more easily. The fact that there was little change in sites of cancer spread suggests that these cells may be more resistant and so need to be targeted with a different treatment to the primary tumor.”

Dr. Joanna Reynolds, Cancer Research UK’s director of centers, said, “A important aim of Cancer Research UK’s Experimental Cancer Medicine Network is to support the development of tests that can help doctors to quickly spot treatment resistant cells in the tumor, so therapy can be tailored appropriately. Advanced ovarian cancer can be very difficult to treat, meaning it’s vital that patients are monitored closely to ensure they are benefitting from treatment. We’re excited to be funding the next stage of this research, which will look at the potential benefits of this test in a much larger group of patients. ”

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