Initial neutrophil-to-lymphocyte ratio predicts radiation-induced trismus in parotid gland cancer

Objective: To investigate the link between pretreatment neutrophil-to-lymphocyte ratio(NLR) and the incidence of radiation-induced trismus(RIT) in parotid gland cancers(PGC) patients after postoperative radiotherapy(PORT). Method: Data of PGC patients who had oral examinations before and after PORT were reviewed retrospectively. We comprised patients who had maximum mouth opening (MMO) assessments before and after PORT and complete blood count test on the first day of PORT. MMO of ≤35 mm was considered as RIT. The receiver operating characteristic (ROC) curve analysis was used to search for an ideal NLR threshold value that might be linked to RIT rates. Results: Fifty-one patients were included, with a RIT incidence of 15.7%. The NLR cutoff that showed a link with the prevalence of RIT in the ROC curve analysis was 2.7[Area under the curve (AUC):82.0%; sensitivity:87.5%; specificity:74.4%]. The patients were divided into groups based on this value:Group 1: NLR≤2.7 (N = 34) and;NLR >2.7 (N = 17). In comparative analysis, the incidence of RIT was found to be statistically higher in the NLR >2.7 than counterpart (35.2%vs.5.8%;r_s:0.79; p <.001). Also, a mean temporomandibular joint dose ≥51.0Gy was linked to increased RIT rates (p <.001). Conclusion: This study showed that high pre-PORT NLR levels were a robust and independent predictor of significantly elevated rates of RIT.