Preliminary Study on Differences in Systemic Immune-Inflammation Index and Its Prognostic Correlation in Synovial Sarcoma

Abstract Objective To analyze the differences in molecular characteristics and the systemic immune-inflammation index (SII) among different subtypes of synovial sarcoma (SS) through a comparative study, and to preliminarily evaluate the value of SII in assessing the malignancy degree of SS and predicting patient prognosis. Methods Clinical data of SS patients who underwent surgery at The First Affiliated Hospital of Nanjing Medical University between January 2010 and January 2024 were retrospectively analyzed. Recurrence-free survival (RFS) and overall survival (OS) served as the primary endpoints for prognostic evaluation. Statistical analysis was performed using SPSS software. The log-rank test was used to assess significant differences between groups. Univariate and multivariate analyses were conducted to identify factors influencing patient SII values and prognosis, thereby evaluating the utility of SII in determining the malignancy degree of SS and predicting patient outcomes. Results This study included 37 SS patients. The follow-up period ranged from 6 to 154 months, with a mean of (68.05 ± 37.07) months. The cohort comprised 17 males and 20 females, with a mean age of (47.54 ± 15.19) years. Primary tumor sites included the upper limb (11 cases), lower limb (15 cases), groin (8 cases), abdominal wall (1 case), intra-abdominal region (1 case), and thoracic spine (1 case). There were 26 monophasic SS cases and 11 biphasic SS cases. During follow-up, recurrence occurred in 16 cases (11 monophasic, 5 biphasic), and metastasis occurred in 6 cases (2 monophasic, 4 biphasic). The 5-year recurrence-free survival rate was 42.1%, and the 5-year overall survival rate was 91.3%. Univariate analysis suggested that surgical margin and tumor type were factors influencing RFS, while surgical margin was a factor influencing OS. Furthermore, correlations were observed between tumor type, recurrence/metastasis status, and SII values. Among 15 patients with tumor volume < 5 cm, 7 were initially misdiagnosed by imaging (4 by ultrasound suggesting benign, 3 by MRI suggesting benign), yielding an imaging misdiagnosis rate of 46.67%. The mean SII value in this group was (524.75 ± 155.22). Among 18 patients with tumor volume ≥ 5 cm, 2 were misdiagnosed (1 by ultrasound as neurogenic tumor, 1 by MRI as a cyst), resulting in a misdiagnosis rate of 11.11%. The mean SII value for this group was (701.42 ± 167.60). Additionally, 4 patients had multiple SS, and tumor size was not measured. Correlation analysis between SS subtype, tumor size, prognosis, and SII values revealed statistically significant associations (P < 0.05). Conclusion SII holds indicative significance for the diagnosis of synovial sarcoma. A high SII often indicates high malignancy and may help reduce the misdiagnosis rate for small tumors that are easily mistaken for benign lesions. Simultaneously, a high SII is frequently associated with poor prognosis, necessitating more careful comprehensive treatment planning for affected patients. Thus, SII is significantly important for the diagnosis of synovial sarcoma and for predicting patient prognosis.