The University Record, December 19, 1995

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Nonsurgical method of diagnosing spread of breast cancer being evaluated by U-M researcher

By Bruce Weintraub
Medical Center Public Relations

Each year approximately 200,000 American women are diagnosed with breast cancer. Most of them will have surgery to determine whether the cancer has spread to the lymph nodes under the arm.

A U-M researcher has been awarded a $4.3 million grant by the National Cancer Institute for a national study to determine whether positron emission tomography, or PET scanning, can supplement or replace lymph node dissection as a diagnostic tool.

PET scanning is a newer imaging method that uses a trace amount of radioactivity to look at tumor metabolism. Breast cancer, similar to many other cancers, has an increased metabolic rate for glucose, meaning it uses more sugar than normal tissues.

"We inject a radiolabeled glucose molecule intravenously and follow it with the PET scanner, which is very sensitive to small amounts of radioactivity," explains Richard L. Wahl, professor of internal medicine and of radiology. "By following the scan, we can determine where spots are in the body that have increased glucose metabolism. These spots, or markers, often represent cancer cells."

The five-year study will be conducted at three sites, including the Medical Center. More than 400 newly diagnosed breast cancer patients will be enrolled in the trial and receive a PET scan to determine whether the primary breast cancer tumor cells have spread to the adjacent lymph nodes. Patients also will undergo standard axillary lymph node dissection to confirm the results obtained from the PET scan.

"The hope from this study is that PET scanning will prove to be an accurate method of determining if cancer has spread from the breast," Wahl notes. "Ultimately, we believe that up to 70 percent of breast cancer patients may be spared surgery on the lymph nodes if the study proves successful."

Wahl says that there recently has been an increasing trend to a more conservative management of breast cancer by performing a lumpectomy---which involves the removal of the breast cancer lump, and surrounding tissue---instead of a mastectomy, or removal of the entire breast.

"Whether a lumpectomy or mastectomy is performed, it is important to know if the axillary lymph nodes are involved in order to gauge the actual spread of the cancer," Wahl says. "Until now, the only way to find out if the cancer has spread is to surgically remove them by performing a lymph node dissection and looking at them under a microscope."

He adds that lymph node dissection is generally a safe procedure, but side effects, such as numbness, discomfort, arm swelling and occasional infections of the affected arm, are not uncommon.

Wahl says another goal of the study will be to follow breast cancer patients for an extended period after their initial PET scan to see how accurate PET is in determining a patient's prognosis.

"The prognostic information provided by PET may help oncologists and others caring for breast cancer patients determine which patients need chemotherapy and which ones don't," he adds.

According to Wahl, PET scanning also has substantial potential for aiding oncologists in diagnosing numerous other types of cancers, including lung, colorectal, melanoma and lymphoma.