Exercise therapy for cancer treatment-induced trismus in patients with head and neck cancer: A systematic review and meta-analysis of randomized controlled trials

Background: Trismus is a common complication of cancer treatment, particularly radiotherapy, for head and neck cancer. We investigated whether exercise therapy could prevent or manage limited mouth opening in patients before or after the cancer treatment. Methods: We performed a systematic review and meta-analysis to evaluate the effectiveness of exercise therapy combined with a jaw-mobilizing device in the prevention and treatment of cancer treatment-induced trismus. The electronic databases PubMed, EMBASE, CINAHL, and Cochrane Central Register of Controlled Trials were searched for articles on trismus published before July 2020 with no language restrictions. The primary outcome for prevention was trismus incidence. The treatment outcome for trismus was the improvement of maximal interincisal opening (MIO). Results: Thirteen randomized controlled trials (RCTs) involving 733 patients were identified. Six studies assessed MIO and found that exercise therapy adjuvant to the use of a jaw-mobilizing device significantly improved the MIO from 4.48 (95% confidence interval [CI] = 0.20, 8.75) to 14.20 (95% CI = 10.73, 17.67) mm. Seven studies evaluating the preventive outcome of incidence of trismus found no significant difference between standard usual care and exercise therapy adjuvant to the use of a jaw-mobilizing device (risk ratio = 1.20; 95% CI = 0.61, 2.34). Conclusions: The current evidence from RCTs revealed that exercise therapy can lead to MIO improvement following the development of cancer treatment-induced trismus, but does not prevent trismus in patients being treated for head and neck cancer. The clinical exercise programs used in the studies were heterogeneous; therefore, additional high-quality RCTs are required.