Using PET/CT in the Detection of Breast Cancer Metastases

About one-third of women diagnosed with early-stage breast cancer will have their cancer travel, or metastasize, to other parts of the body, with the bone being the most common site of initial detectable spread. Controversy continues to surround the question of whether CT and bone scans should be standard in evaluating patients for these metastases, or whether integrated PET/CT scanning might be more effective at detecting breast tumors that have reached nearby bones.

Results from a recent retrospective study conducted by Memorial Sloan-Kettering Cancer Center investigators suggest that PET/CT scanning might offer the most efficient and effective detection of newly diagnosed breast cancer that has spread to the bone. The new findings may mean less stress and more timely therapy for patients, and could make the longtime use of radionuclide bone scans for breast cancer obsolete in this setting.

Detecting Breast Cancer's Spread

Of the approximately 200,000 cases of early stage breast cancer diagnosed in the United States each year, one in three will eventually spread to other parts of the body. In nearly half of these women, the first detectable distant site is the bone. (Distant sites can include any location in the body other than the lymph nodes located closest to the primary tumor.) Yet there is no standard approach for the detection of such metastases.

Bone scans, positron emission tomography (PET), and computed tomography (CT) all continue to be employed alone or in combination for the detection of breast cancers suspected to have spread. In some cases, physicians use all three imaging techniques. Each has its own strengths. For example, bone scans detect bony regions in the process of growth or repair, which can be a sign of metastatic disease. PET, on the other hand, assesses irregularities of biochemical activity in the body, such as cells that metabolize glucose unusually fast. Such behavior is a trademark of a cancer cell. Meanwhile, CT creates anatomical images that can help physicians isolate and analyze the size and shape of tumors.

With one machine, simultaneous PET/CT draws on the strengths of each tool to both detect and locate abnormal and potentially cancerous cells. Further, its diagnostic reach can go beyond the bone. "In contrast with bone scans, which are only able to detect bone metastases, PET/CT has the advantage of concurrently imaging other common sites of breast cancer metastases such as the liver and lungs," says lead author Patrick Morris, a breast cancer specialist at Memorial Sloan-Kettering. "Therefore, PET/CT may not only be superior to bone scan for the detection of bone metastases, it may also be more convenient for patients."

Could PET/CT be powerful enough to jettison the need for additional testing? Are bone scans simply redundant?

A Retrospective Study