A 67-year-old man comes to the physician with a 3-week history of right shoulder pain. The pain is dull, occurs mostly at night, and is poorly responsive to over-the-counter analgesics. He has had no trauma to his shoulder. His past medical history is significant for hypertension, type 2 diabetes mellitus, and chronic lower back pain. The patient is a lifetime nonsmoker. His last hemoglobin A1c was 8.2%, and prostate-specific antigen checked a few weeks ago was 22 ng/mL (normal

Question

A 67-year-old man comes to the physician with a 3-week history of right shoulder pain.  The pain is dull, occurs mostly at night, and is poorly responsive to over-the-counter analgesics.  He has had no trauma to his shoulder.  His past medical history is significant for hypertension, type 2 diabetes mellitus, and chronic lower back pain.  The patient is a lifetime nonsmoker.  His last hemoglobin A1c was 8.2%, and prostate-specific antigen checked a few weeks ago was 22 ng/mL (normal <4 ng/mL).  On physical examination, the right shoulder has full range of motion and no local tenderness.  There is decreased vibration sense at both ankles and first metatarsal heads.  Digital rectal examination shows an enlarged nodular prostate.  Plain radiographs of the right shoulder show no abnormalities.  Results of a transrectal prostate biopsy are pending.  Which of the following is the best next step in management of this patient's shoulder pain?

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Explanation: 11ec2b69_bf59_b38b_8f63_e17fc5a2f9b3_MD0005_00 This patient, with new musculoskeletal pain in the context of an ongoing evaluation for likely prostate cancer, has a significant risk of bony metastasis. Prostate cancer metastases target bone preferentially, especially the axial skeleton where there is the largest percentage of red marrow. Pain from bone metastasis is typically dull and aching or boring in character, and symptoms often occur at night. Patients with bone metastases often have unremarkable findings on physical examination and plain x-rays, and additional imaging studies are usually needed. Imaging modalities in skeletal metastasis are dependent on whether the lesions are primarily osteolytic, osteoblastic, or mixed: Malignancies with primarily osteolytic metastases (eg, multiple myeloma) are poorly visible on radioisotope (technetium-99 MDP) bone scans as the labeled technetium is preferentially taken up in areas of new bone formation. Plain x-rays and positron emission tomography (PET) are usually more effective. Malignancies with primarily osteoblastic metastases (eg, prostate cancer) are easily seen on radioisotope bone scans. Malignancies that have mixed lytic/blastic metastases (eg, breast cancer) are usually seen on bone scans, but PET may be helpful in some cases. Because most prostate cancer metastases are osteoblastic, radioisotope bone scans are very sensitive for identifying skeletal lesions. In the absence of local pain, bone scan is not necessary for the routine staging of low-grade prostate cancer. However, it should be considered in patients with possible high-grade disease (eg, prostate-specific antigen >20 ng/mL, Gleason score >8, extraprostatic extension). bone scans (Choice A) CT is generally very sensitive for identifying soft-tissue metastatic disease in the chest, abdomen, or pelvis. However, it is less sensitive than bone scan for bony metastasis of prostate cancer. (Choice B) Dual energy x-ray absorptiometry is used to measure bone density (osteoporosis/osteopenia screening) and may assist in deciding whether to initiate androgen-deprivation therapy in patients with prostate cancer (due to the risk of further bone loss with therapy). It is not useful in staging the disease or evaluating acute musculoskeletal pain. (Choice D) Physical therapy is used in treating a wide variety of traumatic and nontraumatic musculoskeletal disorders. For example, frozen shoulder (adhesive capsulitis) frequently occurs in diabetics and can be treated effectively with physical therapy. However, this patient has full range of motion at the shoulder and no local findings to suggest a disorder that is amenable to physical therapy. Once the diagnosis is clear, referral for physical therapy can be reconsidered. (Choice E) Gabapentin is used in the long-term treatment of neuropathic pain, such as post-herpetic neuralgia or painful diabetic neuropathy. It is also used as an adjunctive measure for chronic pain of other causes. However, it is highly unlikely that neuropathy would present with dull, aching focal pain in a proximal upper extremity. Gabapentin alone also would not be effective in treating cancer pain from metastatic bone disease; other medications, such as nonsteroidal anti-inflammatory drugs or opioids, would be more effective. Educational objective: Radioisotope bone scans detect areas of increased bone turnover and are very sensitive for osteoblastic bone metastases of prostate and other cancers. References: Diagnostic and therapeutic use of radioisotopes for bony disease in prostate cancer: current practice. (http://www.ncbi.nlm.nih.gov/pubmed/17302562)

A 67-Year-Old Man Comes to the Physician with a 3-Week