[The assessment and management of cancer pain]

The accurate assessment of pain is essential in cancer pain treatment. As pain is a subjective experience, there is no precise method to quantitate it objectively. There are two approaches: the first is the use of laboratory techniques to measure the patient's reaction to experimental pain, such as sensory decision theory analysis. This method is a psychophysical procedure to distinguish between a person's criteria for reporting pain and the sensory experiences induced by noxious stimuli. The second is the use of tools to assess pain by the patient's description. Many kinds of rating scales, including visual analogue scales, have been used to evaluate the intensity of clinical pain, but they cannot assess the quality of pain. For the specification of both qualitative and quantitative properties of clinical pain, the McGill Pain Questionnaire (MPQ) was constructed using 102 words that patients use to describe pain. The sensitivity and usefulness of the MPQ are no longer in doubt, but it cannot be used in Japan as such because of the difference in cultural background and language. Listening carefully to the patient's complaint is required not only for the precise assessment of pain, but also is a form of psychological treatment. Cancer pain should be relieved as soon as possible. Although WHO cancer pain relief is the first choice, nerve blocks and intraoperative radiotherapy, if indicated, must be taken into consideration in the early phase of the pain treatment.