Temporal muscle thickness (TMT) is an independent prognostic parameter in patients with newly diagnosed brain metastases (BM) of breast cancer (BC)

Abstract

Background: Sarcopenia has been described as objectively measurable parameter indicating frailty and adverse prognosis in several cancer types. We thus hypothesized that TMT may serve as surrogate marker of frailty. Methods: 189 BC patients (luminal A: 45/189 (23.8%); HER2: 75/189 (39.7%); triple negative: 35/189 (18.5%); unknown subtype: 34/189 (18.0%), all female with a median age of 54 years (range 30-85) and newly diagnosed BM were identified from a BM database. Clinical characteristics including survival times were retrieved from chart review. Diagnosis specific graded prognostic assessment (DS-GPA) was calculated based on clinical characteristics. Baseline TMT at diagnosis of BM was measured in MRI (axial plane of isovoxel (1x1x1mm), T1 - weighted images) at diagnosis of BM. Results: Median TMT was 5.4 mm (range 1.65 - 10.50 mm) and showed no correlation with age (correlation coefficient -0.341; p 0.001 or Karnofsky performance status (correlation coefficient 0.213; p = 0.003), as well as no difference in dependence of cortisone treatment (p = 0.994) at BM diagnosis. Survival analysis using a Cox regression model was performed using baseline TMT diameters to predict survival time (HR 0.810; 95% CI 0.735-0.892; p 0.001). Patients with a higher baseline TMT presented with an improved survival prognosis. In detail, risk of death was reduced by 19% with every additional millimeter of baseline TMT. Further analysis was performed by the means of a Cox regression model including TMT and DS-GPA as covariates (TMT: HR 0.790; 96% CI 0.703-0.889; p 0.001; DS-GPA: HR 1.426; 95% CI 1.154-1.762; p = 0.001). In the multivariate model TMT prediction of survival was nearly unchanged with a reduced risk of death of 21 % with every additional millimeter of baseline TMT. Conclusions: TMT, which can serve as a surrogate parameter of sarcopenia, is an independent predictor of survival in patients with newly diagnosed BC BM. TMT is easily and reproducibly assessable in routine MR images and may help to better define frail patient populations and may thus facilitate patient management by supporting patient selection for therapeutic measures or clinical trials.