Abstract
Skeletal muscle radio-density (SMD) measures muscle radiation attenuation (in Hounsfield Units, HU) on computed tomography (CT) scans. Low SMD is prognostic of poor survival in melanoma, however its significance is unknown for hematologic malignancies. We performed a single institution, retrospective review of all follicular lymphoma (FL) patients who received chemoimmunotherapy from 2004–2009. Patient demographics, FL International Prognostic Index 1 (FLIPI-1), progression free (PFS) and overall survival (OS) were collected as primary endpoints. Objective response rates (ORR) were secondary. SMD was calculated using pre-treatment CT scans. In 145 patients reviewed, median values were age 59, FLIPI-1 of 2, stage III, and 8 chemoimmunotherapy cycles received. Median PFS for those with low SMD (<36.6 and <33.1 HU for patients with BMI ≤ 25 and > 25 kg/m2, respectively) compared to those with high SMD was profoundly worse, 69.6 vs. 106.7 months (hazard ratio [HR] 1.85; p = 0.01), respectively. Median OS was not reached in patients with high SMD vs. 92.7 months in low SMD patients (HR 4.02; p = 0.0002). Multivariate analysis supported lower SMD’s OS detriment (HR = 3.40; p = 0.002) independent of FLIPI-1 (HR 1.46–2.76, p = 0.05) or gender. Low SMD predicted lower ORR, 83 vs. 96% (p = 0.01). SMD predicts survival independent of FLIPI-1 and potentially chemoimmunotherapy response. SMD is an inexpensive and powerful tool that can complement FLIPI-1.
Highlights
Weight loss is considered a poor prognostic indicator across many diseases
It was not until emergence of CD20-directed therapy that gender became recognized as a prognostic factor [16]
Our findings in an unselected follicular lymphoma (FL) population find higher skeletal muscle (radio)-density (SMD) measured by computed tomography (CT) is associated with improved progression free survival (PFS) and overall survival (OS)
Summary
Weight loss is considered a poor prognostic indicator across many diseases. More recently, work into what contributes to this poor prognosis has led to investigation of body composition, a study of the proportion of lean and fat tissues in the human body. Though severe loss of skeletal muscle mass (sarcopenia) is prognostic in oncology [1,2,3,4], skeletal muscle (radio)-density (SMD) has been found to be prognostic across multiple tumor subtypes [4,5,6]. Low SMD, has an appearance of ectopic fat infiltration. This phenomenon has been assessed on pre-treatment CT images and was recently found to be predictive of outcomes in metastatic renal cell cancer and melanoma independent of targeted therapy use [5, 6]. The value of what constitutes low SMD is dependent on body mass index (BMI) given that fatty infiltration of muscle is more prevalent in overweight and obese individuals [4]
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