CXI was calculated as follows:
CXI = (SMI x Alb) / NLR
where SMI is the skeletal muscle index, Alb is the serum albumin in g/dL and NLR is the neutrophil-to-lymphocyte ratio (absolute neutrophil count/absolute lymphocyte count).
In order to estimate the effect of CXI on OS and PFS, we dichotomized CXI at the median value of 35 into stage I and stage II cachexia groups in the analysis. Age was also dichotomized into age <60 years and age >60 years. Descriptive statistics such as means and proportion were presented for continuous and categorical variables, respectively.
Student’s t-test, the chi-square test, or Fisher’s exact test, where it was appropriate, was used to compare the difference between groups. The Kaplan–Meier method and log-rank test were used to estimate and compare survival between factors.
The Cox proportional hazard model was used to estimate the risk ratio in univariate and multivariate analysis. Statistical software SAS 9.4 (SAS Institute Inc.) was used for data management and statistical analyses. All two-sided P-values , 0.05 were considered statistically significant.
The study was performed after obtaining approval from Louisiana State University Institutional Review Board (IRB). The research complied with the principles of declaration of Helsinki.
After a review of nearly 400 charts, a total of 112 patients with complete medical information and follow-up were included in the final analysis.
Most patients were excluded due to insufficient medical information. Table 1 summarizes the characteristics of patient population. The median age for the entire group was 57 years. Half of all the patients were African Americans, which is consistent with the demographics of the city. Two-thirds of the participants were men; 55% of all cancers were adenocarcinoma and the rest were different histologies (squamous, large cell, NSCLC [not otherwise specified]).
|Table I – Patient characteristics with advanced non-small cell lung cancer.|
|Age (Median, Range)||N = 112(%) 57 (34–88)|
|African American||58 (52)|
|Number of metastatic sites|
|No chemotherapy||39 (35)|
|Any chemotherapy||73 (65)|
|Response to chemotherapy|
|Any response||27 (24)|
|Stable disease||14 (13)|
|Progression of disease||25 (22)|
|Decline in performance status||46 (41)|
|Median progression free survival||3.8|
|Median overall survival||5.4|
Only one patient was positive for epidermal growth factor receptor (EGFR) mutation. Two-thirds of the patients had good PS (0–1), which is not expected as all of them were newly diagnosed. Half of the patients had only one to two sites of metastatic disease, and 35% did not receive any chemotherapy.
Median PFS for all the patients was 3.8 months, and OS was 5.4 months (Table 1). CXI values ranged from 1.08 to 248. CXI as a continuous variable is statistically significant in predicting PFS and OS when the change of CXI is one unit (data not shown). The hazard ratio (HR) changes are about 1% when the CXI changes in one unit for PFS and OS.