MRI tops current standard for bone metastases from prostate cancer

A study by researchers from Boston and Brussels has found MR imaging more accurate than bone scintigraphy and x-rays for detection of bone metastases from prostate cancer. MRI could boost staging and management of these patients in a cost-effective way.

Clinical literature shows about 85% of patients with advanced prostate cancer develop bone metastases that lead to skeletal complications such as pain and fractures and require invasive management. These high-risk patients usually undergo bone scans and x-rays and sometimes other imaging tests, but the metastatic lesions go undetected in many cases despite the time, costs, and risks involved with ionizing radiation.

MRI could provide a more accurate staging of these patients and would also avoid unnecessary operations, said principal investigator Dr. Frédéric E. Lecouvet, a professor of musculoskeletal radiology at the University of Louvain's Saint Luc University Hospital in Brussels, Belgium.

"A proportion of patients with negative bone scans and x-rays do have bone metastases at MRI, which indicates that local invasive and debilitating surgery is useless," he said.

Lecouvet and colleagues from Louvain and Harvard University prospectively enrolled 66 consecutive patients with a high-risk prostate cancer profile who underwent MRI in addition to a standard sequential imaging workup. The imaging workup included technetium-99m bone scintigraphy, targeted x-rays in patients with inconclusive bone scans, and on-request MRI in patients with inconclusive bone scans and x-rays.

The investigators compared all clinical, biological, and imaging data at baseline and after six months of follow-up. They found that MRI alone was more sensitive than the combination of the other tests (J Clin Oncol 2007;25[22]:3281-3287).

Forty-one patients had bone metastases. The sensitivity of bone scans (46%), combined scintigraphy/x-ray (63%), or combined scintigraphy/x-ray/MRI (83%) did not match the 100% sensitive of MRI performed alone (p<0.05). The specificity of MRI to bone metastases was 88% compared with 32% for bone scans, 64% for combined scintigraphy/x-ray, and 100% for combined scintigraphy/x-ray/MRI.

MRI identified metastases in about a third of patients considered negative and almost half of those with inconclusive results by standard imaging. MRI outcomes modified therapy in these cases.

"This better identification of patients with mets may in turn help early systemic treatment and administration of validated drugs, which will be particularly interesting if MRI also enables lesion measurements and evaluation of response to therapy as my team showed in another recent paper," Lecouvet said.

The study suggests that MRI is a powerful, accurate approach in this setting. Its success depends, however, on whether insurance companies and Medicare are willing to pay for it, said Dr. Michael M. Graham, director of the University of Iowa's nuclear medicine program and the SNM's vice president-elect.

"The implications of the study largely hinge on the cost-effectiveness. In Belgium, because of reimbursement, it's actually less expensive to go with the MRI approach compared with the standard sequential workup. But in other countries, including the U.S., it's quite the opposite," Graham said.

For more information from the Diagnostic Imaging archives:

Whole-body imaging brings new slant to cancer staging

Prostate MRI adds brains to cancer treatment brawn

Whole-body MRI attracts MSK imagers

Whole-body MR imaging outclasses bone scans