Efficacy of Myofascial Pain Syndrome Treatment in Patients With Cancer in Palliative Care

This is a clinical trial designed as a comparative, randomized, single-blinded intervention study. Patients will be recruited from wards and radiotherapy sector of the Ribeirão Preto Clinical Hospital - Ribeirão Preto Medical School, University of São Paulo (FMRP-USP). Initially, patients aged 50 years or older with cancer in palliative care will be evaluated to assess the prevalence of myofascial pain syndrome using Travel and Simons' diagnostic criteria and for the following variables: demographic characteristics, functional status (Palliative Performance Scale), pain intensity (visual analog scale and pain threshold measurement with a pressure gauge), prognostic score (Palliative Prognosis Score), depression and anxiety (Hospital Anxiety and Depression Scale), quality of life (European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core 15 PAL) and analgesic drugs in use. The participants that (1) accomplish the Travel and Simons' diagnostic criteria for myofascial pain syndrome, (2) have performance status on the Karnofsky scale of 30 or more, and (3) have pain intensity on visual analog scale of 5 or more will be randomized for the clinical trial. The sample size calculation resulted in 15 participants for each group, totaling a sample composed of 30 patients. The intervention group will be submitted to the trigger point injection procedure with 1% lidocaine, and the control group will receive usual care, defined as the treatment for pain prescribed by their assistant doctors. Both groups will be reevaluated after 72 hours and 1 week after the procedure. In the analysis statistics, chi-square test (or Fisher's exact test) will be used to evaluate categorical variables. For the comparison between the groups at each moment (before and after intervention) will be used the linear mixed effects model. The significance level established was \<0.05. SAS Statistical Software (version 9.3; SAS Institute, Inc. Cary , NC) will be used for the analysis.