The Impact of Low Skeletal Muscle Mass and Density on Patients with Head and Neck Cancer Receiving Concurrent Chemoradiation

Abstract

Sarcopenia (decrease in skeletal muscle) is a predictor of poor prognosis in cancer patients. Head and neck cancer patients are at risk for sarcopenia from nutritional compromise from their disease. Skeletal muscle index (SMI) and skeletal muscle density (SMD) are measures of sarcopenia that can be obtained from diagnostic imaging studies. While SMI has been studied in head and neck cancer, SMD is thought to be a more specific marker for poor outcomes and has not been previously reported in this population. To better understand the impact of SMD in head and neck cancer, we conducted a review of patients receiving concurrent chemoradiation and assessed outcomes with respect to SMI and SMD. Medical records of consecutive patients treated for histologically-proven head and neck cancer at a single center between 2011 and 2015 were reviewed. All patients received concurrent chemoradiation. Chemotherapy varied per medical oncology discretion. Measurements of SMI and SMD were obtained from treatment planning computed tomography (CT) scans using previously published methods. Image analysis was performed by a single, blinded observer using NIH ImageJ software. SMI was calculated as the cross-sectional area of the paravertebral and sternocleidomastoid muscles at a single axial CT slice at the level of the C3 vertebral body, while SMD was calculated using the mean radiation attenuation at the same level. Thresholds for low SMI and SMD were defined based on previously validated criteria. Overall survival (OS) and progression-free survival (PFS) were calculated using the Kaplan-Meier method with comparison between groups performed using the log-rank test. Association between patient factors and survival was calculated in univariate and multivariate analysis. Two hundred and twenty-two patients met criteria for inclusion. Median follow-up was 31 months (range 1-73 months). The most common subsite was oropharyngeal cancer (63%). Post-op patients comprised 24% of the sample. Fifty-six percent of patients met criteria for low SMI and 38% met criteria for low SMD. Thirty-nine percent of patients experienced chemotherapy delays of >1 week and 36% missed radiation days due to toxicity. There was no difference in OS (p=0.93) or PFS (p=0.33) between patients with low versus normal SMI. Patients with low SMD had significantly worse OS (p=0.01) and PFS (p=0.02) compared to those with normal SMD. On multivariate analysis, age>60 (p=0.03), radiation delays (p=0.01), low albumin (p=0.01), and low SMD (p=0.04) were all associated with decreased OS, while radiation delays (p<.01) and low SMD were associated with decreased PFS (p=0.04). Low SMD is associated with worse cancer-related outcomes in patients with head and neck cancer receiving concurrent chemoradiation and may serve as a stronger predictor for poor survival than low SMI.