Background: Despite the suggestion of a relationship between development or progression of myofascial pain syndrome (MPS) and psychological stress, few studies have reported its proportion or association with treatment efficacy. Objective: We aimed to investigate the proportion of MPS with psychological stress among cancer patients and to compare the efficacy of trigger point injection (TPI) in the same patients with/without psychological stress. Design: This was a prospective observational study. Setting/Patients: Participants were 205 patients with cancer who received TPIs for MPS at a hospital in Japan. Results: The proportion of patients with MPS and psychological stress was 0.57 (95% confidence interval [CI] 0.50-0.64). The TPI efficacy rate at seven days after treatment was 0.55 (95% CI 0.46-0.64) for patients with MPS and psychological stress and 0.82 (95% CI 0.74-0.90) for their counterparts without psychological stress (p < 0.004). The odds ratio for TPI efficacy seven days after treatment with psychological stress versus without psychological stress was 0.25 (95% CI 0.13-0.49). Conclusions: MPS was a clinical symptom of psychosomatic disorder in approximately half of our patients. The TPI efficacy for patients with MPS who had psychological stress was lower than for their counterparts without psychological stress. Trial registration: UMIN000041210. Registered 27 July 2020 (retrospectively registered).
Keywords: cancer patients; myofascial pain syndrome; psychological stress; psychosomatic disorder; trigger point injection.