Diagnostic imaging of bone metastases

PURPOSE: To present an "algorithm" for detection and diagnosis of skeletal metastases, which may be applied differently in symptomatic and asymptomatic cancer patients. MATERIAL AND METHODS: February to March 1999 we randomly selected and retrospectively reviewed the clinical charts of 100 cancer patients (70 women and 30 men; mean age: 63 years, range: 55-87). All the patients had been staged according to TNM criteria and had undergone conventional radiography and bone scan; when findings were equivocal, CT and MRI had been performed too. RESULTS: The primary lesions responsible for bone metastases were sited in the: breast (51 cases), colon (30 cases: 17 men and 13 women), lung (7 cases: 6 men and 1 woman), stomach (4 cases: 2 men and 2 women), skin (4 cases: 3 men and 1 woman), kidney (2 men), pleura (1 woman), and finally liver (1 men). The most frequent radiographic pattern was the lytic type (52%), followed by osteosclerotic, mixed, lytic vs. mixed and osteosclerotic vs lytic patterns. The patients were divided into two groups: group A patients were asymptomatic and group B patients had local symptoms and/or pain. DISCUSSION: Skeletal metastases are the most common malignant bone tumors: the spine and the pelvis are the most frequent sites of metastasis, because of the presence of high amounts of red (hematopoietic active) bone marrow. Pain is the main symptom, even though many bone metastases are asymptomatic. Pathological fractures are the most severe consequences. With the algorithm for detection and diagnosis of skeletal metastases two different diagnostic courses are available for asymptomatic and symptomatic patients. Bone scintigraphy remains the technique of choice in asymptomatic patients in whom skeletal metastases are suspected. However this technique, though very sensitive, is poorly specific, and thus a negative bone scan finding is double-checked with another physical examination: if the findings remain negative, the diagnostic workup is over. On the contrary, in patients with a positive bone scan or with local symptoms and pain, radiography and CT are used for screening of metastatic lesions: results may be negative (for low sensitivity of conventional radiology) or questionable (in which case bone biopsy is necessary), or else symptoms may be due to different causes than metastatic lesions (i.e., osteoarthritis). Before bone biopsy is made, MRI must be performed, because it is the only technique that allows to distinguish between bone marrow components. The limitation of MRI is the poor specificity of its findings, which may provide misleading findings.