What is the most urgent diagnostic and initial management step for an elderly male with known prostate cancer on therapy who presents with posterior neck pain and limited neck mobility?

Urgent MRI of the Cervical Spine is Mandatory

In an elderly male with prostate cancer on androgen deprivation therapy presenting with posterior neck pain and limited neck mobility, you must immediately obtain MRI of the cervical spine to rule out spinal cord compression from metastatic disease—this is a neurologic emergency that can result in permanent paralysis if not detected and treated urgently. 1

Why This is Critical

• Spinal cord compression is a devastating complication of metastatic prostate cancer, and early detection is critical for successful management 1
• Prostate cancer commonly metastasizes to bone, particularly the spine, and vertebral metastases with posterior neck pain represent a red flag for impending or actual cord compression 1
• A retrospective analysis showed that MRI identified cord compression in 16% of patients with metastatic prostate cancer and back pain who had no overt neurologic symptoms, with radiological evidence of spinal cord compromise in an additional 11% 1
• MRI is the preferred and most sensitive imaging technique for detecting soft-tissue abnormalities and spinal cord compression 1

Immediate Diagnostic Approach

First-Line Imaging

• Obtain MRI of the cervical spine without delay—do not wait for plain radiographs or other studies 1
• MRI should be performed urgently (within hours, not days) given the risk of neurologic deterioration 1
• The European Society for Medical Oncology specifically recommends MRI of the spine to detect subclinical cord compression in men with castration-resistant prostate cancer (CRPC) with vertebral metastases and back pain 1

Key Clinical Red Flags to Assess Immediately

• Evaluate for any neurologic deficits: weakness, sensory changes, bowel/bladder dysfunction, or gait disturbances 1
• Limited neck mobility combined with pain in a patient with known metastatic potential is highly concerning 1
• Patients on androgen deprivation therapy have increased risk of bone metastases and skeletal-related events 1

Concurrent Management Considerations

While Arranging Urgent MRI

• Initiate high-dose corticosteroids (typically dexamethasone 10-16 mg IV) if there is any clinical suspicion of cord compression, even before imaging confirmation 1
• Consult neurosurgery and radiation oncology immediately if MRI confirms cord compression 1
• Do not delay imaging to obtain plain radiographs first—MRI is the definitive study 1

Treatment Implications Based on Findings

• If cord compression is confirmed, external beam radiation therapy should be offered urgently (single 8 Gy fraction has equal pain-reducing efficacy to multifraction schedules for bone metastases) 1
• Surgical decompression may be indicated depending on the degree of compression, neurologic status, and spinal stability 1
• For patients with bone metastases from CRPC at high risk for skeletal-related events, denosumab or zoledronic acid should be initiated (denosumab delays skeletal-related events longer than zoledronic acid, though neither prolongs survival) 1

Common Pitfalls to Avoid

• Do not attribute neck pain to "arthritis" or "muscle strain" in a patient with known prostate cancer—always assume metastatic disease until proven otherwise 1
• Do not start with plain radiographs or CT—these will delay definitive diagnosis and miss early cord compression 1
• Do not wait for neurologic symptoms to develop before imaging—by the time weakness or sensory changes appear, irreversible damage may have occurred 1
• Recognize that patients on androgen deprivation therapy have increased fracture risk and bone complications, making skeletal metastases more likely 2

Disease Context

• Approximately 10% of prostate cancer patients present with metastatic disease, which has a 5-year survival rate of 37% 3
• Bone is the most common site of metastatic prostate cancer, and vertebral involvement can lead to catastrophic neurologic complications if not detected early 1
• The patient's treatment status (androgen deprivation therapy) suggests either metastatic hormone-sensitive or castration-resistant disease, both of which carry significant risk for skeletal metastases 4, 2