# The Association Between Skeletal Muscle Mass and Surgical Site Infection and Prognosis in Patients Undergoing Free Flap Reconstructive Surgery for Oral Squamous Cell Carcinoma: A Single-Center, Retrospective Study

## TL;DR

This study found that lower skeletal muscle mass and extranodal extension are linked to worse survival in patients undergoing surgery for oral cancer.

## Contribution

The study identifies SMI and ENE as independent predictors of survival in OSCC patients undergoing free flap reconstructive surgery.

## Key findings

- Low SMI was associated with significantly worse overall survival (60.2% vs. 81.1%).
- SMI and extranodal extension were confirmed as independent predictive factors for survival.
- SSI rates were not significantly different between low and high SMI groups.

## Abstract

Skeletal muscle mass (SMM) loss is a poor prognostic factor in older patients and those with cancer. We determined the SMM index (SMI), rates of surgical site infection (SSI), and prognosis of 92 patients (59 males and 33 females) with oral squamous cell carcinoma (OSCC) who underwent resection and free flap reconstructive surgery (FFRS) from 2013 to 2021. Preoperative computed tomography measured SMM at L3. Patients were classified into low (n = 47, 51.1%) and high SMI (n = 45, 48.9%) groups by median. SSI occurred in 11 (12.0%) patients, and wound dehiscence and delayed wound healing occurred in 22 (23.9%). Rates of SSI did not differ significantly between the low and high SMI groups. Cox multivariate analysis included SMI (low vs. high; hazard ratio [HR]: 2.339, 95% confidence interval [CI]: 1.008–5.429; p = 0.015) and extranodal extension (ENE) (present vs. none; HR: 7.727, 95% CI: 3.083–19.368; p < 0.001). SMI and ENE were identified as independent predictive factors of overall survival in patients undergoing FFRS for OSCC.

Background/Objectives: Local and systemic factors, including nutritional status, influence the prognosis of oral squamous cell carcinoma (OSCC). Skeletal muscle mass (SMM) loss is a poor prognostic factor in older patients and those with cancer. Herein, we examined the SMM index (SMI), rates of surgical site infection (SSI), and prognosis of 92 patients (59 males and 33 females) who underwent resection and free flap reconstructive surgery (FFRS) between 2013 and 2021. Methods: Preoperative computed tomography was performed to measure SMM at L3. The median SMI was 45.94 and 38.03 cm2/m2 in males and females, respectively. Patients were classified into low and high SMI groups based on median SMI, and overall survival (OS) was analyzed. Results: Overall, 47 (51.1%) and 45 (48.9%) patients had low and high SMIs, respectively. SSI occurred in 11 (12.0%) patients; wound dehiscence and delayed wound healing were observed in 22 (23.9%). SSI rates were not significantly different between the low and high SMI groups. Conversely, OS was significantly associated with age, pathological N (pN), extranodal extension (ENE), and SMI (high, 81.1%; low, 60.2%). Univariate analyses revealed significant associations between OS and age (≥65 vs. <65 years), SMI (low vs. high), pN (present vs. none), ENE (present vs. none), and albumin (<4.0 vs. ≥4.0 mg/dL). Cox multivariate analysis included SMI (low vs. high; hazard ratio [HR]: 2.339, 95% confidence interval [CI]: 1.008–5.429; p = 0.015) and ENE (present vs. none; HR: 7.727, 95% CI: 3.083–19.368; p < 0.001). Conclusions: SMI and ENE were identified as independent predictive factors of OS in patients with OSCC undergoing FFRS.