Cancer pain

A 65-year-old woman presents to her family physician with abdominal discomfort. Work-up quickly reveals a diagnosis of cancer of the pancreas with local invasion of the upper lumbar spine and destruction of the L1 vertebral body (Figure 48.1). Her previous medical history is significant only for hypertension and hyperlipidemia. She reports her pain as originating in the epigastrium and radiating through to the back. It is described as aching in character, constant in nature, and rated at 6/10 on a Numeric Rating Scale. Her only analgesic to date has been acetaminophen 500 mg 4 times daily. She notes some fatigue on exertion and a slight decrease in her appetite. A review of systems is negative for nausea, vomiting, or constipation. 1. What is the etiology of cancer pain? Our patient has a solid tumor that can directly invade the tissues and organs of the body, causing pain. The invasion posteriorly of the cancer into the spine, with destruction of the lumbar vertebral body, is causing the constant cancer pain. The exact physiology of bone pain is not fully understood, but may involve proliferation of osteoclast cells by tumor-induced release of acids, or excitation of nociceptors by prostaglandins and other factors released by the tumor stroma.[1] In addition, the cancer cells in bone may stimulate sensory neuron sprouting within the bone marrow resulting in painful sensation transmission.[1] Pain that is caused by direct invasion of organ and tissue is usually classified as nociceptive pain. Cancers may also directly invade nerves and nerve plexuses resulting in pain, classified as neuropathic pain. Invasion of the celiac plexus by the pancreatic cancer produces a vague abdominal visceral pain, while invasion of a brachial plexus from apical lung cancer will produce neuropathic pain of the upper extremity.[2] This pain related to direct invasion of nerve tissue is often described in terms such as burning, tingling, electric, or shooting. It may be somewhat more resistant to management with standard opioid and non-opioid analgesic therapies.