Pilot Study on the Effect of Intrathecal Opioids on Immune Function in Humans With 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