How is chronic pain classified in cancer patients?
Chronic pain in patients with cancer is categorized according to whether it is tumor related, treatment related, or unrelated to the cancer. Tumor-related pain may occur at the site of the primary tumor or at a site of metastasis. Treatment-related pain can be secondary to the use of chemotherapeutic agents (peripheral neuropathy), radiation therapy (radiation plexitis, myelopathy, or secondary tumors), or surgery (postmastectomy syndrome, radical neck syndrome, postthoracotomy syndrome). Approximately 10%–15% of the pain syndromes that occur in cancer patients are unrelated to the underlying cancer and cancer treatment.