Prevalence and Stress Involvement of Myofascial Pain Syndrome Across Cancer Stages: A Multicenter Prospective Observational Study with Exploratory Analyses of Tension-Type Headache, Migraine, and the Armchair Sign.

Background: Functional somatic syndromes are common causes of noncancer-related pain in patients with cancer. Nonetheless, the prevalence and stress involvement in representative conditions, including myofascial pain syndrome (MPS), tension-type headache (TTH), and migraine (MG), remain insufficiently described. The Armchair Sign is a physical examination maneuver used to evaluate stress-related muscle tension. Objective: To assess stage-specific prevalence and stress involvement of MPS in patients with cancer, with secondary exploratory analyses of TTH, MG, and the association between the Armchair Sign and stress involvement. Design: Multicenter prospective observational study. Setting/Subjects: A total of 1277 patients diagnosed with cancer at three palliative care centers. Results: Cancer stages were survivorship, initial treatment, additional treatment, and best supportive care. Pain was reported by 71.7% (cancer-related, 47.2%; noncancer-related, 43.5%); among them, stress involvement was identified in 60.5%. MPS, TTH, and MG were diagnosed in 12.7%, 7.4%, and 3.5%, respectively. Among those, stress involvement was identified in 48.8% (MPS), 80.0% (TTH), and 71.1% (MG). In the survivorship stage, TTH (17.4%) and MG (7.2%) were more prevalent than in other stages ( Conclusions: MPS and stress involvement were frequent among patients with cancer across cancer stages. TTH, MG, and the Armchair Sign findings should be interpreted as secondary exploratory findings, and they require further validation.