(P 389) THE ROLE OF NUTRITIONAL STATUS ON POSTOPERATIVE AND ONCOLOGICAL OUTCOMES IN RETROPERITONEAL SARCOMA

Objective: Recent studies have highlighted the crucial role of nutritional status on outcomes of retroperitoneal sarcoma (RPS). This study aims to clarify the impact of malnutrition and sarcopenia on postoperative complications and oncolocical outcomes in RPS patients.

Methods: A retrospective, single-center cohort study was conducted at the Sarcoma Surgery Unit of IRCCS Humanitas Research Hospital, Rozzano (Milan, Italy). Patients with primary or recurrent RPS who underwent surgery from January 2010 to June 2023, were included. Preoperative data included demographics, medical history, comorbidities (assessed by the Age-adjusted Charlson Comorbidity Index), and anthropometric data. Body Mass Index (BMI) cutoffs were used to classify patients as underweight (BMI < 18.5 kg/m²), and obese (BMI ≥30 kg/m²). Nutritional status was categorized using Onodera's Prognostic Nutritional Index (OPNI) and Skeletal Muscle Index (SMI), with malnutrition identified by median OPNI and sarcopenia thresholds based on published standards. Intraoperative and postoperative data included operative time (OT), blood loss, resection completeness, complications (Clavien Dindo Classification), reoperation rates, and length of hospital stay (LOS). Kaplan–Meier analysis and Cox proportional hazards models analyzed survival data. Statistical significance was set at p< 0.005.

Results: A total of 256 patients were analyzed (46.1% female; 53.9% male). Median age was 64 years (IQR 53-73). The median OPNI was 48 (IQR 44-52), identifying 50.2% (120/239) as malnourished. The median SMI was 44.1 (IQR 37.8-50.9), with 53.2% (75/141) classified as sarcopenic. Median tumor size was larger in primary tumors (170mm, IQR 104.5-260) compared to recurrent tumors (83mm, IQR 51-120). Liposarcoma was the most frequent histological subtype (65%, n=160). Tumor grading revealed 46.1% (n=96) Grade 1, 28.4% (n=59) Grade 2, and 25.5% (n=53) Grade 3 tumors. Complications occurred in 54% of patients (n=135), with CDC  3 in 22% (n=55). Reoperation was required in 13.25% (n=33), and median LOS was 11.5 days (IQR 8-21). Table 1 shows the differences between groups based on their nutritional status.
Malnutrition was significantly associated with presentation (p < 0.001), increased use of neoadjuvant treatments (p < 0.001), larger tumor size (p < 0.001), histology (p=0.005), higher tumor grades (p=0.016), and lower 5-year overall survival (OS) as calculated by Sarculator (p=0.008).
Sarcopenia was significantly associated with male sex (p=0.001), coronary artery disease (p=0.035), and lower BMI (p=0.005).
Univariate analysis (Table 2) showed significant associations of severe postoperative complications with malnutrition (OR 2.128, p=0.021), with each unit reduction in OPNI increasing the odds by 5.2% (OR 0.948, p=0.018). SMI and sarcopenia did not significantly correlate with severe complications.
According to the survival analysis (Figure 1), malnutrition was significantly associated with poorer survival (p=0.002); sarcopenia did not significantly affect OS (p=0.587).
Lower PNI was significantly associated with worse OS (HR 0.955, p=0.008 for primary tumors; HR 0.898, p=0.023 for recurrent tumors), while SMI was only significantly associated with OS in primary tumors (HR 1.020, p=0.043).

Conclusion: This study underscores the critical impact of nutritional status on postoperative outcomes and survival in RPS patients. OPNI is a valuable prognostic tool for assessing malnutrition and predicting complications and survival, whereas SMI and sarcopenia require further evaluation. Comprehensive nutritional assessments should be integrated into routine care for RPS patients to improve clinical outcomes.