The goal of this observational study is to investigate the correlation and quantitative relationship between the analgesic effect of fentanyl transdermal patches in cancer pain patients and their nutritional status.

Cancer-related pain is one of the most common and unbearable symptoms among patients with malignant tumors. Opioids are commonly used to treat moderate or severe cancer pain. Among them, fentanyl is a synthetic opioid with analgesic adjuvant with a 50~100 times higher potency than morphine. Due to its small molecular weight, high lipid solubility, and low irritation to the skin, transdermal fentanyl (TDF) is formulated, which is more convenient for patients with intestinal obstruction, swallowing difficulties, and intolerance to oral opioids. According to some research, the TDF demonstrated good cancer pain control for patients switching from morphine or oral oxycodone preparations, and was well tolerated.

However, a part of patients still go through increased breakthrough pain, sleep disturbances, and even accompanied by anxiety and depression when using TDF. Therefore, early identification of cancer pain patients using TDF at risk of ineffectiveness is an essential step in increasing analgesic effectiveness, and improving quality of life.

Some studies discovered different clinical factors such as age, gender, serum albumin, glomerular filtration rate, kidney disease, body mass index (BMI), total protein, alanine aminotransferases have some influence on fentanyl serum concentration and the dose of TDF. Furthermore, the clinical factors seem to have a greater impact on the effectiveness of TDF than the genetic factors which may affect the liver metabolism of fentanyl. Based on these results, we aim to investigate the correlation and quantitative relationship between the analgesic effect of fentanyl transdermal patches in cancer pain patients and their nutritional status. Our purpose is to help clinicians recognize and increase the analgesic effect of TDF according to the patient's risk level.

Inclusion Criteria:

• Cancer pain patients admitted to our hospital;
• Cancer pain patients switched from oral sustained-release strong opioid analgesics to fentanyl transdermal patches during the hospital stay.

Exclusion Criteria:

• Patients who have been switched to fentanyl transdermal patches after titration with an analgesic pump;
• Patients using fentanyl transdermal patches in combination with other oral sustained-release strong opioid analgesics;
• Patients using fentanyl transdermal patches in combination with an analgesic pump;
• Patients who have used fentanyl transdermal patches for less than 3 days;
• Patients with postoperative pain;
• Patients with allergies;
• Patients who are pregnant women;
• Patients with missing data.

Inpatient at the oncology hospital