(P 352) OUTCOMES OF PRIMARY INTRATHORACIC SOFT TISSUE SARCOMA

Objective: To evaluate outcomes for patients with primary intrathoracic sarcomas, defined as sarcomas of the lung, pleura, and mediastinum, excluding the chest wall.

Methods: A retrospective review was conducted on patients treated at a specialized sarcoma center between January 2007 and May 2022. We included all patients with primary sarcomas in the thorax, including those with localized or metastatic disease at the diagnosis. Overall survival (OS) was analyzed using Kaplan-Meier survival analysis, with differences between groups assessed using the log-rank test. The cumulative incidence of local recurrence (LR) and distant metastasis (DM) was estimated using competing risks analysis, considering death as a competing event. Differences between groups in cumulative incidence were assessed using Gray's test. Cox proportional hazard models computed hazard ratios (HRs) for survival outcomes.

Results: We identified 47 adult patients (55% male) with a median age at diagnosis of 51 years (range 34 - 68.5). Median follow-up was 36.1 (95% CI: 29.1, 92.7) months. Among all patients, 80.9% had localized intrathoracic disease, and 19.1% had metastatic disease at diagnosis. Tumour sizes were as follows: 6.4% (n=3) were less than 5 cm, 23.4% (n=11) were 5-10 cm, and 40.4% (n=19) were greater than 10 cm; data for 14 patients (29.8%) were missing. The majority of tumours (59.6%) originated in the pleura/lungs/diaphragm, 12.8% (n=6) in the mediastinum, 12.8% (n=6) were in the cardiac region, 10.6% (n=5) in the vessels, and 4.2% (n=2) were in the esophagus. Synovial sarcoma (10.6%), undifferentiated sarcoma (6.4%), and malignant solitary fibrous tumour (6.4%) were the most common histologies; 25.5% of patients had grade II-III tumours, 10.6% had grade 1 tumours, and data were missing for 63.8% of patients. Among patients with localized disease (n=38), 79% (n = 30) underwent surgical resection (Sx), 13.2% (n=5) received preoperative radiation (RT), and 18.4% (n=7) received postoperative RT; 15.8% (n=6) patients who received neoadjuvant chemotherapy (CT). 43.3% (13/30) of patients had positive surgical margins. The median OS of the entire cohort was 30.19 [95% CI: 0.4,0.7] months. Patients with metastatic disease at diagnosis had significantly worse survival than those with localized disease, with a hazard ratio (HR) of 6.27 (95% CI: 1.89, 21.0); p=0.003. In patients with localized disease, the disease recurred in 19 patients (50%); 3 patients (7.9%) had local recurrence (LR) only, and 16 patients (34.1%) had both local and distant recurrence. The 1-year cumulative incidence of LR was 37.0% [95% CI: 19.8, 54.2], the 1-year cumulative incidence of distant metastasis (DM) was 28.1% [95% CI: 11.94%, 44.31%], and the OS rate was 80.9% [95% CI: 69.1, 94.7]. There were no significant differences in LR (p=0.785) or DM (p=0.834) among patients who underwent surgical resection, comparing those treated with surgery alone, surgery plus RT without CT, surgery plus CT without RT, and those who underwent surgery with both CT and RT.

Conclusion: In this small retrospective cohort of patients with intrathoracic sarcoma, neither neoadjuvant/ adjuvant RT nor CT was associated with rates of LR and DM. Multi-center prospective investigations are required to assess the optimal management of intrathoracic sarcomas.