Opposed-phase MRI less accurate in detecting treated metastasized spinal cancers

Pennsylvania researchers discovered opposed-phase MRI imaging is less accurate in detecting treated spinal metastases compared to those lesions that are untreated.

While authors note opposed-phase imaging can accurately differentiate untreated and treated spine metastases from benign lesions, treatment—radiation specifically—lessens the sensitivity and accuracy of detecting a cancerous growth from a benign one.

In a study published online Feb. 2 in Academic Radiology, authors point out that detecting between the two is often challenging using MRI, but doing so is important due to the poor prognosis that accompanies advanced stage disease of spinal metastases.

“Mistakenly proposing that a lesion is a spinal metastasis when it is a benign lesion may result in biopsy of the lesion or, in some cases, may alter the potential therapy available to the patient and consequently affect patient survival,” wrote Michael T. Perry, MD, and Ronnie Sebro, MD, both from the department of radiology at the University of Pennsylvania.

In the retrospective study, analysis was performed in 101 patients who underwent opposed-phase MR spine imaging. Of those, 25 benign lesions were analyzed, 25 untreated spinal metastases and 89 treated spinal metastases.

Lesions were placed under out-of-phase and in-phase MR sequences, and the signal intensity ratio (SIR) of the lesions was calculated. SIR numbers were compared between the three lesion groups mentioned above, and the signal receiver operator characteristic (ROC) curves were used to distinguish between benign lesions and untreated spinal masses.

Crucial findings from the study include:

• Benign lesions had lower mean SIR than untreated and treated spinal metastases.
• A cutoff SIR of 0.856 had an accuracy of 88.00% for untreated lesions, 77.5 percent for previously treated lesions, and 70.5 percent for previously radiated lesions.
• The ROC curve to differentiate benign lesions from radiated spinal metastases was significantly different from the ROC curve to differentiate benign lesions from untreated spinal metastases.
• The ROC curve to differentiate benign lesions from lesions treated with chemotherapy only was significantly different from the ROC curve to differentiate between benign lesions and radiated spinal metastases.

“[B]oth untreated and treated spine metastases can be differentiated from benign lesions using opposed-phase imaging; however, treatment, in particular radiation therapy, reduces the sensitivity and accuracy of opposed-phase imaging for correctly differentiating whether a lesion is a spinal metastasis or a benign lesion,” wrote Perry et al.