Unraveling Self-Reported Signs of Central Sensitization in Breast Cancer Survivors with Upper Limb Pain: Prevalence Rate and Contributing Factors

Background: Hypersensitivity of the central nervous system to environmental and chemical stimuli is a clinical feature of central sensitization mechanisms that can be assessed with the central sensitization inventory (CSI).

Objective: The aim was to determine prevalence rate of this feature and explore the treatment-, patient-, pain-, and psychosocial-related variables associated with the degree of self-reported signs of central sensitization, assessed with the CSI (0-100), in breast cancer survivors at long-term.

Study Design: Cross-sectional study.

Setting: University Hospitals, Leuven, Belgium.

Methods: One hundred and forty-six women with persistent pain, more than one year after breast cancer surgery, were included. The following factors were analyzed by bivariable and multivariable analysis: 1) treatment-related variables (type of surgery, levels of lymph node dissected, radiotherapy, chemotherapy, hormone therapy, and trastuzumab); 2) patient's related variables (age and body mass index); 3) pain-related variables (pain intensity, pain quality, primary hyperalgesia, and index of widespread pain); and 4) psychosocial variables (the degree of pain catastrophizing and vigilance and awareness to pain). The dependent variable was degree of central sensitization measured with the CSI. Additionally, a stepwise regression was performed.

Results: Fifty-five (38%) patients reported signs of central sensitization measured with the CSI (i.e., > 40/100). From multivariable analysis, it appears that more severe pain quality and higher levels of pain catastrophizing contribute to a higher degree of central sensitization. The stepwise regression revealed that up to 24% of variance of the CSI can be explained by these factors.

Limitations: A selection bias may be present since patients were all recruited from a larger cohort participating in clinical trials on the effectiveness of physical therapy after breast cancer treatment.

Conclusion: Signs of central sensitization cannot be neglected in breast cancer survivors at long term. More severe pain quality and pain catastrophizing contribute to higher levels of central sensitization in this population.

Key Words: Breast neoplasm, pain, central sensitization mechanisms, central sensitization inventory.