A 54-year-old man presents with a one-month history of left hip pain. He is employed as an automobile mechanic and slipped on a patch of wet flooring. He was able to catch himself from falling but in doing so felt a sharp pain in the lateral aspect of his left hip. He continued to work after the injury despite having significant pain and limitations secondary to the injury. Anteroposterior (AP) radiograph of the left hip obtained in the office reveals a fracture of the greater trochanter. He denies history of cancer, weight loss, or fatigue. Magnetic resonance imaging of the hip is performed and shows a lytic osseous lesion within the left greater trochanter, extending to the surrounding soft tissue. What is the next best step in treating this patient?
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CT imaging with contrast of the chest, abdomen, and pelvis was performed to determine the primary source of the patient’s metastasis of unknown origin. A bone scan was also ordered to determine if other bones were involved. CT scans revealed left and right adrenal masses, an enlarged right kidney, and multiple pulmonary nodules consistent with renal cell carcinoma with metastatic disease to the lungs and adrenal glands. Complete metabolic panel, complete blood count (CBC), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) were also ordered. Pertinent laboratory results included slight anemia with a hematocrit of 35% and elevated CRP and ESR levels.
Any new destructive bone lesion found in a patient older than 40 years should be evaluated for metastatic disease, myeloma, and lymphoma first. The most likely cause of a malignant-appearing bone mass in patients older than 40 years is metastatic disease, with lung metastases being the most common source. The mnemonic “bacon, lettuce, tomato, kosher, and pickle” is often used to remember the breast, lung, thyroid, kidney, and prostate as the most common sources of metastatic disease. The most common site of bony metastases is the thoracic spine, and the most common site of pathological fracture resulting from metastases is the proximal femur. Thyroid and prostate metastases tend to be the least aggressive and slow growing, with a median survival of 48 and 40 months, respectively. Survival rates for breast cancer metastases can vary widely but average approximately 24 months. Patients with kidney and lung metastases have the poorest prognosis, with mean survival as low as six months.
The work-up of a solitary bone lesion requires a detailed history and physical examination. Patients may report a history of prior cancer, bowel or bladder changes, or weight loss. Physical examination of the breasts, skin, chest, prostate, and neck/thyroid is important as it may uncover lymphadenopathy, costovertebral tenderness, abdominal masses, or breast masses that may help identify the primary source. Neurologic deficits may indicate spinal cord or nerve root compression from a metastatic lesion.
Initial laboratory work-up should include CBC with differential, ESR, CRP, complete metabolic panel, urine analysis, and coagulation studies. Serum protein electrophoresis can be considered if multiple myeloma is suspected, serum carcinoembryonic antigen assessment if colon or pancreatic cancer is suspected, and serum cancer antigen 125 can be obtained if there is a risk of ovarian cancer.
Initial imaging work-up for a solitary bone lesion of unknown etiology includes AP and lateral radiographs of the affected area, as plain radiographs provide the best diagnostic value of all imaging modalities. CT scan with contrast of the chest, abdomen, and pelvis helps to identify the primary source and can be used in staging the patient’s disease. A bone scan is important in the work-up of a solitary tumor to help differentiate a primary bone tumor vs multiple lesions from metastatic disease. Positron emission tomography (PET)/CT measures metabolic activity such as blood flow, oxygen use, and glucose metabolism to pinpoint the location of abnormal activity produced by a cancerous tumor. PET/CT is more specific for metastatic disease than bone scan. PET/CT is also used to monitor response to therapy. A bone survey, or skeletal survey, is a series of radiographs of the major bones in the body including the skull, ribs, spine, pelvis, and long bones. A skeletal survey is a useful test to evaluate bony involvement in patients with known multiple myeloma as bone scans may be falsely negative in 30% of individuals with this condition.
Many orthopedic healthcare providers have different thresholds for when to refer patients and when to continue with further work-up of a solitary bone lesion of unknown etiology. If a primary malignant bone tumor is considered in the differential diagnosis, referral to an orthopedic oncologist is recommended. However, in a patient older than 40 years with a solitary bone lesion, a metastatic carcinoma is approximately 500 times more likely than a primary bone sarcoma. A thorough work-up can help avoid inappropriate referral and expedite treatment, which improves patient care.
- Bueker PJ, Rothrock CP. Current management of skeletal metastasis. Orthop Knowl Online J. 2010;8(8). http://orthoportal.aaos.org/oko/article.aspx?article=OKO_ONC015#abstract. Accessed July 14, 2015.
- O’Donnell P. Metastatic cancer of bone. http://www.orthobullets.com/pathology/8045/metastatic-cancer-of-bone. Accessed July 14, 2015.