International Association for the Study of Pain describes pain as 'An unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage' (1). The phenomenon of pain is a common and underdiagnosed distressing symptom, resulting from the interaction between neural pathways and neurochemical mediators. An important group that suffers from acute and chronic pain -both at the beginning of the disease and in the later stages- are pediatric cancer patients. It is known that more than half of all children with cancer experience moderate to severe pain. Management of pain in childhood cancer plays an important role in patients’ life quality and compliance with their treatment. Moreover, it is thought that uncontrolled pain may have negative effects on immune system functions, wound healing, tumor growth, and gastrointestinal functions through cortisole and neurochemokines that occur as a result of pain (2).
Pain can be categorized into three types for determining the etiology which may guide treatment choices:
Nociceptive pain: Tissue injury and inflammation cause activation of nociceptors by inflammatory mediators and activate neurons that transmit the pain. Bone metastasis and mucositis are examples of this group. ‘Somatic Nociceptive pain’ is typically well localized and described as sharp, aching, squeezing, stabbing, or throbbing. Visceral Nociceptive pain’ is often described as dull or crampy.
Neuropathic pain is caused by nerve injury (resulting from compression, transection, infiltration, ischemia, or metabolic injury to the nerves) and can be described as burning, scratching, tingling or with numbness.
Nociplastic pain occurs without evidence of tissue or nerve damage. The mechanisms are not well understood. It is thought that dysfunction of the pain signals of central nervous system plays a role (1).
Assessment of the severity of pain in children is more difficult than adults and it is related to the child's age, cognitive ability and clinical condition. Observational– behavioral scales consider child's reaction to pain for younger children or cognitively impaired patients. The most common scales are FLACC (used for children < 3 years), facial expressions in the Wong-Baker pain scale for 3-8 ages, and numericale valuations in the Wong-Baker pain scale for children older than 8 years (3).
Multidisciplinary and individualized pain management incorporating pharmacological and non-pharmacological (cognitive-behavioral and supportive therapies) can be more effective for pain. Pharmacological therapy varies depending on the child's age, pain intensity, drug's pharmacokinetics and response to previously administered agents. The World Health Organization analgesic ladder algorithm facilitates the choice of the appropriate drug. Acetaminophen and nonsteroidal anti-inflammatory drugs are the first choice for mild pain. Opioid agents (morphine, hydromorphone, oxycodone, hydrocodone, fentanyl, methadone) should be used for moderate to severe pain. Analgesics should be used orally whenever possible and adverse effects of opioids (eg, pruritus, constipation) should be carefully monitored.
