The purpose of this study is to examine the changes in immune function, as measured by biomarkers in the blood, that happen with intrathecal (spinal) delivery of opioid medications for the treatment of moderate to severe cancer pain.

Hypothesis: Treatment of pain with intrathecal (spinal) therapy is associated with little alteration of immune function as measured by biomarkers in the blood of cancer patients with moderate to severe pain.

Biomarkers of immune function will be measured before and after patients receive an intrathecal pain pump for management of cancer pain.

Inclusion Criteria:

• Diagnosis of cancer
• Evaluation by a pain management physician and confirmation that cancer is the primary etiology of patient's pain
• Moderate to severe pain, as specified by a baseline Pain Rating Score of 5 or above on a scale from 0 (no pain) to 10 (worst pain imaginable) despite current opioid therapy
• Pain management plan (as developed by Interventional Pain Service, patient and primary service) that includes placement of an intrathecal drug delivery system for pain management
• Able and willing to give informed consent

Exclusion Criteria:

• Patients with an expected life expectancy of less than 12 weeks
• Patients not felt be a safe surgical candidate by pain management physician for placement of and intrathecal drug delivery system (IDDS) due to the presence of severe medical comorbidities
• Patients who are not a candidate for intrathecal drug therapy due to coagulopathy, concurrent necessary use of blood thinners, presence of systemic infection, drug allergy to analgesic agent, evidence of CSF obstruction or other technical factor
• Severe or untreated psychiatric disease
• Refusal of informed consent
• Pregnant patients or patients less than 18 years of age

Patients with cancer-associated pain who are receiving an intrathecal pump for management of cancer pain