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Dr. Katia Tonkin is assessing estrogen levels in women with metastacized breast cancer to determine the value of hormone therapy versus chemotherapy in their individual cases.


Tonkin, a senior medical oncologist at Edmonton’s Cross Cancer Institute as well as an associate professor with the University of Alberta, works extensively on clinical trials.

In one of her latest trials, funded through the Alberta Breast Cancer Research Initiative, Tonkin will follow 100 patients whose cancer has become metastatic—that is, at some point after the initial diagnosis and treatment, the cancer has returned, this time spreading to another part of the body such as the liver, the lung or, most commonly, the bone.

Typically, such patients have from a few months to a few years to live.

Tonkin and her colleagues are using a relatively new and innovative type of positron emission tomography (PET) scanning that looks at estrogen levels. Traditionally, PET scans involve injecting a small amount of radioactive glucose (sugar) into a vein and then using a scanner to make detailed, computerized pictures of areas inside the body where the glucose is used. Because cancer cells often use more glucose than normal cells, the pictures can be used to find cancer cells in the body.

But many cancers are also fed by estrogen and can be treated with hormone therapy, which is considered far less invasive than chemotherapy and avoids side-effects such as hair loss. When breast cancer is first diagnosed, the cancers are tested to see if they are hormone-positive and therefore likely to respond to hormone therapy.

The problem, says Tonkin, is that hormone therapy is not always effective once a tumour has metastacized. “When you treat them with hormones, only some of the cancer will respond. So let’s say they have a few lumps in their lungs and some in their liver. You might find the ones in the lung shrink very nicely, but the ones in the liver don’t.”

In addition to a traditional glucose-based PET scan, the patients in Tonkin’s study will be examined using a new type of PET scan which measures the sites of breast cancer that take up estrogen. This technology, under development for the past five years, is available in Alberta only on an experimental basis. The point is to measure specific estrogen levels of each individual cancer to make sure that they really would respond to hormone therapy—and to do that before any treatment begins.

Tonkin’s expectation is that, in a significant number of cases, patients whose original cancer tested hormone-positive will learn through this new PET scan that the metasticized cancer is not, in fact, being fed by estrogen. In that event, they will not be given hormone therapy and will instead likely be placed on chemotherapy. The bottom line? “Because we normally wait two or three months to evaluate if a treatment is working,” observes Tonkin, “we could be wasting that time doing something that’s ineffective.” That would be especially tragic for patients who have precious little time to lose.