User talk:Anthonyhcole/Cancer pain

From Fitzgibbon & Loeser 2010, page 6: "Controlling the pain associated with cancer is a major health care problem. The presence of severe pain and other symptoms dramatically affects the quality of life of cancer patients and their families." page 7 "Multiple studies during the 1990s revealed less-than-optimal treatment of pain in patients with cancer. Even with the subsequent availability of more-effective pain treatments ant the publication of pain management guidelines, similar patient care deficiencies continue in the4 United Strates and other countries. The most frequently identified barriers to appropriate pain management in multiple studies have been physician underestimation of the patient's pain, inadequate pain assessment, and patient reluctance to report pain. A growing body of literature attests to the need for significant improvement in cancer pain assessment and treatment in their practice (sic). Poor pain control has been ascribed to lack of expertise by clinicins in assessing and managing cancer pain. [...] Nurses and nursing students are also commonly deficient in their understanding of basic principles of cancer pain management. Studies and expert opinion reveal that comtemporary American medical education does not prepare medical students or residents to provide adequate care for the cancer patient with pain." page 17 "Tumor-associated pain is either nociceptive or neuropathic, or a combination of the two. Nociceptive pain is thought to be related to unhealed tissue injury of either somatic or visceral structures. Pain associated with injury to neural tissues is sustained by aberrant somatosensory processing in the peripheral or central nervous system; it is labeled as neuropathic. An international survey of cancer pain characteristics and syndromes reported that pains thought to be nociceptive and caused by somatic injury occurred in 71.6% of patients, nociceptive visceral pain in 34.7%, and neuropathic pain in 39.7%. Somatic nociceptive pain may be divided into superficial (cutaneous) and deep. Cutaneous pain usually is well localized, sharp, pricking, or burning. Deep tissue pain is usually reported a diffuse and dull or aching in quality. Visceral pain is usually poorly localized, often referred to the body surface, of long duration, and commonly described as 'sickening.' Tumor involvement of the peripheral nervous system has many manifestations and can include lesions within the cerebrospinal fluid space, local invasion, compression of nerves, direct infiltration, perineural spread, and intraneural metastisis, although the last is quite rare." page 18 "Cancer pain is a mixture of acute pain, chronic pain, tumor-specific pain, and treatment-related pain, all compounded by ongoing psychological responses of distress and suffering. Almost all pain in cancer patients may be considered the result of one or more of three fundamental causes: direct tumor involvement, cancer directed therapy, and mechanisms unrelated to cancer or its treatment."

Assessment
page 33 & 34"Many people, both with and without cancer, function quite effectively with a background level of mild pain that does not seriously impair or distract them. As pain severity increases to moderate intensity, a threshold is passed beyond which it is hard for the patient to ignore the pain. The pain now disrupts many aspects of the patient's life. When pain is severe, it becomes a primary focus of attention and prohibits most activities. Pain severity and the degree to which the patient's function is impaired are highly associated."

Pathophysiology/mechanisms
page 33 "The distinction between nociceptive and neuropathic pain is fundamental in assessment because it influences therapy. In principle, pain results from stimulation of nociceptors or by lesions of afferent peripheral or central nerve fibers. Pain is nociceptive if the sustaining mechanisms are related to ongoing tissue pathology. Pain is neuropathic when there is evidence that the pain stems from injury to neural tissues and aberrant somatosensory processing in the periphory or in the central nervous system."

Note: The subheadings are also direct quotes from Fitzgibbon & Loeser.

Tumor involvement of encapsulated organs
page 34"Tumors of the liver, both primary and secondary, are the most frequent examples of tumors of encapsulated organs. These can enlarge the organ to several times the normal size. Since the organ capsule of connective tissue grows less rapidly than the tumor, the intracapsular pressure rises as capsular distention develops. In addition, tumor infiltrates the capsule locally, producing dull, and on rare occasions, stabbing pains. The massive growth of the organ not only stimulates intracapsular nociceptors, but it also irritates larger nerves by pressure or traction on the tissue suspending the organ. Similar organ-enlarging processes in the spleen and kidneys do not lead to pain to the same extent as in the liver, perhaps because of the more stable suspension or embedding of these organs, which are farther away from the midline with its abundant nerve pathways. Kidney tumors produce pain only when the kidney has been almost completely destroyed and the tumor has invaded the pararenal tissue, or when it destroys the renal pelvis. Extrarenal tumor compression on the kidney or ureter can result in severe flank pain. The brain is also an encapsulated organ. Its unique feature is that the bony skull prevents any generalized enlargement after puberty. Pain arises not by destruction of parenchyma but by the increase of intracranial pressure with stimulation of the meningeal and blood vessel nociceptors. Such an increase of intracraneal pressure occurs with space-occupying tumor growth or in focal or generalized brain edema."

Tumor infiltration of peripheral nerves
page 34-35 "Infiltration by tumor tissue is the quintessential tissue trauma stimulus. Indirect damage of unknown pathogenisis might also occur to peripheral nerves in the context of tumor-related conditions (eg, paraneoplastic syndromes). Tumor tissue often infiltrates the perineural cleft, but this does not regularly cause pain. Painful entrapment of the brachial plexus or individual nerves can occur, especially in extensive breast carcinomas and their recurrances ot in chest wall metastases of bronchial carcinomas. The perineural cleft widens with tumor infiltration, and infiltration of the tumor into the nerve itself is common. Degenerative changes of the axis cylinders are sometimes visible with conventional screening methods. Tumor compression regularly elicits pain when the affected nerve cannot give way (eg, a spinal nerve)."

Tumor infiltration of soft tissues
page 35 "Tumor infiltration of soft tissues can cause pain utilizing the mechanisms described above, as with massive infiltration of the retroperitoneum. In addition, infiltration and destruction of mobile structures (eg, the skeletal musculature and tendons and ligaments) can lead to pain via disturbance of function. Here, the tumor spreads in the interstitium and destroys blood vessels, lymphatics, and nerves."

Tumor infiltration of bone
"Infiltration of bone is the most frequent cause of pain in cancer patients. This applies to primary and secondary neoplasias originating from the bone marrow as well as to neoplasms of the bone itself. Such tumors cause pain when they lead to an elevation of the intraosseous pressure, to loss of stability, or to a lesion of the periosteum resulting in periosteal elevation, or with the release of chemical mediators that sensitize nociceptors. The transducers that generate nociception in finely myelenated and unmyelenated axons reside in the bone marrow, in the bone, and in the periosteum. Metasteses frequently lead to extensive bone destruction. Vertebral spread of tumor may involve intervertebral foramina, where nerve root compression can be an additional source of pain. Further spread posteriorly leads to encroachment of the spinal cord and the spinal nerves. In bone, the metasteses primarily located in the bone marrow result in osteolysis or osteosclerosis. Necroses hemorrhages occur frequently in bone metasteses and doubtless play a role in the etiology of pain."

Tumor infiltration of abdominal hollow organs
page 35 "Tumors and their sequelae in the bronchial tree tend to be indolent, whereas those in abdominal hollow organs frequently lead to pain. This applies to all primary and secondary intestinal tumors. There is significant variability in the generation of painfrom intestinal tumors. Pain can be caused by ulcerations, motility disorders, dilations, and disorders of blood flow. In accordance with the extent of the lymphatic tissue, large tumors with extensive ulceration and hemorrhage occur in malignant lymphomas of the gastrointestinal tract. Perineural tumor infiltration, arteritis, or perineural inflammatory reactions are common in tumors of the abdominal and urogenutal hollow organs."

Tumor infiltration and inflammation of serous mucosa
page 35"Pleural carcinomatosis does not usually lead to pain, probably because of the development of pleural effusion, which prevents the pleurae from rubbing together. Peritoneal carcinosis is more frequently associated with pain, and this may be the first symptom of cancer. It stems from either direct contact of the metasteses with peripheral nerves or an inflammatory reaction elicited by carcinomatosis with disorders of visceral motility. Acute inflammatory reactions of the peritoneum with the clinical picture of an 'acute abdomen,' and possibly with empyema, appear after tumor-inducedperforation or penetration of hollow viscera."

Tumor induced necroses in solid organs
page 35"Specific necroses can produce typical pain symptoms in the pancreas. Such necroses, with the typical clinical picture of autodigestive pancreatitis, can occur with pancreatic metastases of a bronchial carcinoma. The autodigestion probably results from tumorous destruction of the parenchyma in conjunction with tumor infiltration and stenoses of the excretory ducts."

Tumor-induced occlusions of blood vessels
page 35"Invasion of the lymphatics and blood vessels is part of the biology of malignant neoplasias and is the precondition for metastisis. Generally, small and peripheral vessels are involved, obstruction of which does not result in any appreciable disorder of the circulation. Larger veins occasionally become infiltrated and occluded. This can lead to edema and pain in the effected area of venous drainage. Infiltration of larger arteries is rare."

Radiation myelopathy, plexopathy and neuropathy
page 102-3"Radiation therapy may cause pain by damage to peripheral nerves, spinal cord, or brain by altering the microvascular connective tissues surrounding peripheral nerve (sic), via fibrosis and chronic inflammationin connective tissues, or bringing about demyelination and focal necrosis of the white and gray matter in the spinal cord. [...] Early-delayed radiation myelopathy occurs from 6 weeks to 6 months after RT, and improvement follows in most cases within 2 to 9 months, although in some instances symptoms may persist for a long period of time. The cervical and thoracic spinal cord is the most commonly involved."