Does magnetic resonance imaging give value-added than bone scintigraphy in the detection of vertebral metastasis?

OBJECTIVE: To determine the role of Magnetic Resonance (MR) imaging for the investigation ofpatients with suspected metastasis to the spine by bone scintigraphy.

MATERIAL AND METHOD: Retrospectively reviewed with comparison was made between Technetium-99m Methylene Diphosphonate (99(m)Tc-MDP) bone scintigraphy and corresponding spine MR images in 48 cases of vertebral metastasis at Siriraj Hospital. The intervals between bone scintigraphy and MR images did not exceed 1 month. The authors studied between January 2005 and December 2006 Bone scintigraphy were performed with planar imaging of the entire body and MR imaging was performed with the 1.5 tesla and 3.0 tesla scanner using standard techniques with T1-, T2-weighted images and fat-suppressed T1-weighted images with intravenous administration of gadopentetate dimeglumine. The MR imaging findings were studied: location (cervical or thoracic or lumbar or sacrum spine), number of lesions (solitary or multiple lesions), pattern of enhancement (homogeneous or inhomogeneous), involvement of spinal canal, compression of spinal cord, extradural extension, other incidental findings such as pulmonary metastasis, pleural effusion, lymphadenopathy The final diagnosis was confirmed clinically and followed-up for further management (radiation or surgery) or followed-up by MR imaging (1 month-16 months) and bone scintigraphy (5 months-12 months).

RESULTS: Forty-eight cases (80 lesions) of vertebral metastasis were identified (25 men and 23 women; mean age 61 years and range 8-84 years). Primary neoplasms include breast cancer (n=11), colorectal cancer (n=7), lung cancer (n=6), prostate cancer (n=5), nasopharyngeal cancer (n=5), head and neck cancer (n=3), thyroid cancer (n=2), liver cancer (n=2), esophagus cancer (n=1), bladder cancer (n=1), retroperitoneum cancer (n=1), medulloblastoma (n=1), cervical cancer (n=1), ovarian cancer (n=1), malignant melanoma (n=1). The result of bone scintigraphy and MR imaging is used to evaluate vertebral metastasis: in 44 lesions of bone scintigraphy positive for vertebral metastasis, 40/44 lesions (91%) which MR imaging reveal vertebral metastasis. This group may not benefit for further investigation by MR imaging. In 24 lesions of negative of bone scintigraphy for vertebral metastasis, the authors found that 14/24 lesions (58%) showed positive of vertebral metastasis from MR imaging. In this group, the authors recommended a further investigation because 58% of negative bone scintigraphy lesions are depicted by only MR imaging. MR imaging demonstrated metastatic cord compression in 16 cases. Extradural extension causes spinal canal narrowing in 30 cases.

CONCLUSION: The authors conclude that the MR imaging is more efficient than the bone scintigraphy in detecting vertebral metastasis, especially in the cases that bone scintigraphy are equivocal or negative for vertebral metastasis in high clinical suspicion. Furthermore, MR imaging is important for the further treatment planning such as radiation therapy or systemic chemotherapy. Although MR imaging is useful in the detection of early metastasis that are localized completely in the bone marrow cavity routinely bone scintigraphy remains that most cost-effective method for examination of the entire skeleton.