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Pain in cancer patients has numerous possible causes. The vast
majority of pain syndromes are caused by direct tumor involvement
of pain-sensitive structures, a smaller number are treatment-related,
and fewer than 10% are unrelated to the cancer. Metastatic
disease may invade bone, obstruct a hollow viscus, and compress
nerve or spinal cord. Radiation treatment may cause fibrosis of
nerve or spinal cord. Chemotherapeutic agents may cause peripheral
neuropathy, aseptic bone necrosis, and predispose to painful opportunistic
infections. Surgical treatment leads to acute postoperative pain,
and may cause deafferentation pain if major nerves or nerve plexi
are cut. In any given patient, one or more of these factors may
be in play, and more than 50% of cancer patients with pain
have more than one source of pain.1
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Primary care physicians and oncologists should be able to recognize
and treat most of cancer-related pain. They should be able to initiate
treatment for the more common causes with opioids and non-opioid
analgesics. More than 70% of patients can be treated effectively
with simple analgesics and adjuvant drugs. Effective pain relief,
without intolerable side effects, is occasionally difficult to obtain
with the use of conventional analgesics. When this occurs, consultation
with a specialist in pain management may be necessary.
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Daut and Cleeland found that while 36% of 286 patients
with nonmetastatic cancer reported pain, 59% of 381 with
metastatic disease did.2 Cleeland and colleagues
found that 67% of 1308 outpatients with metastatic cancer
had pain, and 62% of those had severe pain. Thirty-six
percent reported disability due to pain, and 42% of those
with pain reported inadequate analgesia.3 Terminal
pain, refractory to escalating opioid administration, is a more
challenging problem. Depression, uncontrolled pain, the adverse
effects of opioids, and fear of pain may precipitate suicidal thoughts
or requests for aid in dying.4,5 Pain also adds
to the discomfort experienced by those caring for the dying patient.
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The likelihood of pain associated with cancer depends on the
type and stage of disease. Foley, in a 1-week survey of 540 patients
hospitalized at Memorial Sloan-Kettering Cancer Center, showed that
the prevalence of pain requiring analgesic drugs varies by cancer
type (Table 44-1).6 In contrast, among 1308 outpatients
with metastatic cancer, Cleeland and colleagues did not find variation
in pain prevalence according to cancer type.3
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