Cancer-Related Pain

Incidence

Pain is one of the most common and dreaded symptoms associated with cancer. It occurs in 25% to 50% of patients with newly diagnosed malignancies, up to 55% of patients undergoing treatment, at least 65% of patients with advanced disease, and 40% of cancer survivors. Overall, 75% of patients with cancer experience pain severe enough to require treatment with opioids during their illness. Unrelieved pain directly affects patients' health, daily activities, quality of life, and psychosocial status. The impact of this symptom and the availability of excellent analgesic therapies make it imperative that health care providers be adept at the evaluation and treatment of cancer pain. Ensuring safe and effective pain management while avoiding overuse and potential for aberrant use of opioids is of increasing importance, given the increase in reported cases of opioid overdoses and deaths.

Etiology ( Box 37.1 )

Cancer-related pain is a complex and often recurrent syndrome. Ninety percent of cancer pain can be attributed directly to the tumor or its management, whereas less than 10% is due to unrelated illnesses. In 70% of patients, pain develops when a tumor invades or compresses soft tissue, bone, or neural structures. The common pain syndromes that result are listed in Table 37.1 . The remaining 20% of cancer pain occurs as a result of diagnostic and therapeutic procedures that patients undergo in the process of evaluation and treatment. Examples of these procedures include venipuncture, bone marrow aspiration and biopsy, endoscopy, lumbar puncture, invasive radiologic procedures, surgery, chemotherapy, and radiation therapy.

Surgery is a frequent cause of pain in patients with cancer. Surgical interventions can include biopsy, removal or debulking of a tumor, or management of a complication of the tumor or its treatment, such as a small-bowel obstruction. These procedures may be associated with postoperative pain and injury to local nerves, which can produce chronic pain syndromes that are severe and difficult to manage. Surgically induced nerve injuries are most commonly seen after breast cancer surgery, thoracotomy, radical neck dissection, and limb amputation. Postmastectomy syndrome occurs in 4% to 10% of all women who undergo breast cancer surgery. It is characterized by an early or late onset of a constricting, burning sensation in the posterior arm, axilla, and anterior chest. Postthoracotomy syndrome occurs after nerve injury as a result of rib retraction and typically manifests as an aching, burning sensation in the incisional area with local tenderness, sensory loss, and occasional autonomic changes. Injury to local nerves after a radical neck dissection can produce tightness and burning dysesthesias in the area of sensory loss and lancinating pain. The loss of neck musculature from this surgery can also result in a “droopy shoulder,” thoracic outlet syndrome, and suprascapular nerve entrapment, which may aggravate the underlying pain syndrome.

Chemotherapy and radiation can also produce significant pain in patients with cancer. Phlebitis, mucositis, hemorrhagic cystitis, and peripheral neuropathy are common complications of antineoplastic agents. Immunotherapies may be associated with painful autoimmune complications such as arthritis and colitis. Glucocorticoids, administered as a component of therapy, can cause avascular necrosis of the hip and severe perineal pain when given rapidly in high doses. Bisphosphonates and denosumab, used for management of bone metastases, may cause significant myalgias and arthralgias after administration and can be associated with painful osteonecrosis of the jaw. Examples of radiation-induced pain include mucositis, local skin reactions, enteritis, proctitis, fibrosis with nerve entrapment syndromes, and radiation myelopathy. Patients with malignancies are also predisposed to painful infections, including pneumonia, urinary tract infection and wound infections, candida esophagitis, oral or genital herpes, and herpes zoster.

Pain in patients who are long-term survivors of cancer is an increasingly important topic. Currently more than 4.8% of the population in the United States are cancer survivors, and this rate is rising annually. Prevalence of chronic pain in this population may be as high as 40%. Currently, about 50% of patients with head and neck cancer will become long-term survivors, and 17% of these persons report substantial chronic pain. Up to 20% of breast cancer survivors younger than 40 years who are treated with surgery, radiation, and chemotherapy report significant pain years after treatment has been completed, and this pain appears to interfere with quality of life. Approximately 30% of long-term survivors of lung cancer report substantial pain related to their illness. In addition, hip and sacral pain related to prior treatment with radiation is seen in 30% of long-term gynecologic cancer survivors. Chemotherapy-induced neuropathic pain is also an increasingly important long-term problem for cancer survivors. Of particular importance is emerging information suggesting that inadequately treated acute and chronic pain may predispose long-term cancer survivors to chronic pain syndromes. The American Society of Clinical Oncology (ASCO) has published guidelines to address the burgeoning problem of pain management in cancer survivors.

Current Status of Cancer Pain Management

Studies from hospice and the World Health Organization (WHO) demonstration sites suggest that adequate pain control can be achieved in 85% of patients with cancer pain with oral analgesics. An array of effective options exists for the remaining 15% of patients, including parenteral, transdermal (TD), transmucosal, intranasal, or intraspinal opioids, glucocorticoids, antiinflammatory and adjuvant medications, antineoplastic therapies, and anesthetic and neurosurgical procedures.

Although proper use of available therapeutic approaches should result in excellent pain control in nearly 95% of patients with cancer pain, this pain remains grossly undertreated throughout the world. In most countries, the lack of availability of oral opioids is a major contributing factor. Even in countries such as the United States and in the United Kingdom, where a wide range of opioid analgesics and routes of administration are readily available, studies suggest that cancer pain is undertreated or inadequately treated and that reported pain severity is often moderate to severe. These findings prompted the creation of cancer pain initiatives in most states and the development of cancer pain guidelines and algorithms. In addition, to improve the overall management of pain in the United States, The Joint Commission has revised standards for pain management that are required for continued accreditation.