Evaluation of the Temporal Muscle Thickness as an Independent Prognostic Biomarker in Patients with Primary Central Nervous System Lymphoma

Simple Summary Primary central nervous system lymphoma (PCNSL) is a rare brain tumor with an exceedingly poor outcome. Although some of the established prognostic parameters in PCNSL patients, such as age, blood-related parameters, or the involvement of deep brain structures, are objectively evaluable, the information about the patient's physical condition is still based on the subjective perception of the attending physician. The thickness of the temporal muscle has previously shown to be a biomarker of skeletal muscle quantity and quality, and thus be a potential parameter reflecting sarcopenia, which is a main feature of cancer-related cachexia and a well-known prognostic marker in various disease entities. In the current study we show that temporal muscle thickness is an independent and objectively assessable parameter for outcome prognostication in PCNSL patients and may facilitate the selection and stratification of patients for treatment options or clinical trials in the future. In this study, we assessed the prognostic relevance of temporal muscle thickness (TMT), likely reflecting patient's frailty, in patients with primary central nervous system lymphoma (PCNSL). In 128 newly diagnosed PCNSL patients TMT was analyzed on cranial magnetic resonance images. Predefined sex-specific TMT cutoff values were used to categorize the patient cohort. Survival analyses, using a log-rank test as well as Cox models adjusted for further prognostic parameters, were performed. The risk of death was significantly increased for PCNSL patients with reduced muscle thickness (hazard ratio of 3.189, 95% CI: 2-097-4.848, p < 0.001). Importantly, the results confirmed that TMT could be used as an independent prognostic marker upon multivariate Cox modeling (hazard ratio of 2.504, 95% CI: 1.608-3.911, p < 0.001) adjusting for sex, age at time of diagnosis, deep brain involvement of the PCNSL lesions, Eastern Cooperative Oncology Group (ECOG) performance status, and methotrexate-based chemotherapy. A TMT value below the sex-related cutoff value at the time of diagnosis is an independent adverse marker in patients with PCNSL. Thus, our results suggest the systematic inclusion of TMT in further translational and clinical studies designed to help validate its role as a prognostic biomarker.